Human Growth and Development Discussions

507

14 Learning Outcomes After reading this chapter, you will be able to:

14.1 Define the terms energy balance, positive energy balance, and negative energy balance as they relate to body weight.

14.2 Discuss the factors that contribute to total daily energy expenditure, including basal metabolism, the thermic effect of food, and the thermic effect of exercise.

14.3 Explain how energy expenditure is measured and calculate basal metabolic rate and esti- mated energy requirement using equations and physical activity factors.

14.4 Define the term body composition, and explain the methods used to assess lean body mass and body fat.

14.5 Explain the methods used to estimate a healthy body weight, and the link between body weight and mortality.

14.6 List the criteria used to diagnose eating disor- ders and discuss the shared traits and options for treatment.

True or False? 1. Exercise isn’t necessary to lose weight. T/F

2. Being underweight is always healthier than being overweight. T/F 3. Men burn more kilocalories than women. T/F

4. Body mass index (BMI) can be used to determine if you are at a healthy weight, overweight, or obese. T/F 5. Storing fat around the hips is as

unhealthy as storing it around the waist. T/F

6. Body composition is the same thing as body weight. T/F 7. Eating an excess 100 kilocalories per day will result in a weight gain of a

pound a week. T/F 8. Skinfold calipers are used to measure body composition. T/F 9. Disordered eating and eating disorders are the same thing. T/F

10. Eating disorders can be fatal. T/F See page 535 for the answers.

Energy Balance and Body Composition

508 Chapter 14 | Energy Balance and Body Composition

What Is Energy Balance and Why Is It Important? LO 14.1 Define the terms energy balance, positive energy balance,

and  negative energy balance as they relate to body weight.

The concept of energy balance can be boiled down to five simple words: energy in versus energy out. When the amount of energy (in the form of kilocalories) consumed equals the amount expended, the body does not store excess kilocalories as fat or break down stored fat for energy.

An Energy Imbalance Results in Weight Gain or Loss Body weight remains constant when the energy equation is balanced. If energy intake is greater than the amount of energy expended, the body is in a state of positive energy balance (Focus Figure 14.1). In this situation, weight gain can occur from an increase in muscle mass, an increase in adipose tissue, or both. Positive energy balance is essential during growth periods such as pregnancy, infancy, childhood, and adolescence. Strength training requires a positive energy balance to increase muscle mass, and when the body is in a state of repair following surgery or an illness. However, nonpregnant, healthy adults will experience weight gain if they are in a regular state of positive energy balance. Even a small but chronic positive energy balance can result in weight gain over time. For every 3,500 excess kilocalories consumed, about a pound of body weight is gained. So if an individual takes in 100 excess kilocalories per day, he or she will gain a little less than one pound after a month, and about 10 pounds after a year. Most likely this weight gain will be stored as fat in the adipose tissue.

A negative energy balance occurs when the amount of energy consumed doesn’t meet the amount of energy expended. When inadequate energy is consumed, energy needs are met by mobilizing energy reserves such as stored fat. The result of a negative energy balance is usually weight loss, mostly from adipose tissue. However, some of the weight loss may reflect a decrease in muscle mass, stored glycogen, and water.

The energy balance equation appears to be quite simple. If we would simply consume the same number of kilocalories as we expend, we could maintain a healthful body weight. However, energy balance is more complex than it seems.

Food and Beverages Provide Energy In As you learned in earlier chapters, the kilocalories that make up energy intake come from the carbohydrates, proteins, fats, and alcohol found in foods and beverages. The number of kilocalories found in a given food or beverage can be determined in one of two ways: either in a lab using a bomb calorimeter or by calculating the grams of carbohydrate, fat, protein, and alcohol in the food.

energy balance State at which energy (kilo- calorie) intake from food and beverages is equal to energy (kilocalorie) output for basal metabolism, the thermic effect of exercise, and the thermic effect of food.

positive energy balance State in which energy intake is greater than energy expendi- ture; over time, this results in weight gain.

negative energy balance State in which energy intake is less than energy expenditure; over time, this results in weight loss.

bomb calorimeter Instrument used to measure the amount of heat released from food during combustion; the amount of heat produced is directly related to the number of kilocalories in a given food.

F lip through a magazine, watch a little television, or spend some time online, and before long you’ll find someone talking about how to lose or gain weight. Maintaining a healthy body weight is all about balance—that is, balancing the food and drinks you consume with the amount of kilocalories your

body burns over time. While this equation seems simple enough, food intake is not the sole cause of an

unbalanced equation. Genetics, the environment, and other factors also play a strong role.

In this chapter, we discuss the concept of energy balance, the methods used to assess energy intake

and energy expenditure, and the factors that influence a healthy body weight and body composition.

Head to Mastering Nutrition and watch a narrated video tour of this figure by author Joan Salge Blake.

What Is Energy Balance and Why Is It Important? 509

Figure 14.1 The Concept of Energy BalanceFOCUS

Energy balance is the relationship between the food we eat and the energy we expend each day. Finding the proper balance between energy intake and energy expenditure allows us to maintain a healthy body weight.

Kilocalories out

Kilocalories out

Kilocalories out

Kilocalories in

Kilocalories in

Kilocalories in

ENERGY INTAKE < ENERGY EXPENDITURE = WEIGHT LOSS

ENERGY INTAKE = ENERGY EXPENDITURE = WEIGHT MAINTENANCE

ENERGY INTAKE > ENERGY EXPENDITURE = WEIGHT GAIN

NEGATIVE ENERGY BALANCE When you consume fewer kilocalories than you expend, your body will draw upon your stored energy to meet its needs. You will lose weight.

ENERGY BALANCE When the kilocalories you consume meet your needs, you are in energy balance. Your weight will be stable.

POSITIVE ENERGY BALANCE When you take in more kilocalories than you need, the surplus calories will be stored as fat. You will gain weight.

A chronic state of positive or negative energy balance will result in a change in body weight.

510 Chapter 14 | Energy Balance and Body Composition

▲ Figure 14.2 A Bomb Calorimeter Measures Energy in Foods A bomb calorimeter directly measures the kilocalorie content of food by measuring the heat released during combustion.

Thermometer + –

Water

Stirrer

Ignition wires for heating food

Bomb (reaction chamber)

Food sample

A bomb calorimeter (Figure 14.2) measures the amount of heat produced when a given food is burned. The energy released when the chemical bonds in the food are broken raises the temperature of the water in the calorimeter. Because one kilocalorie is the heat required to raise the temperature of one kilogram of water one degree Celsius, the rise in water temperature indicates the number of kilocalories in the food.

The burning of food also releases carbon and hydrogen, which combine with oxygen to form carbon dioxide and water. Hence, measuring the amount of oxygen consumed during combustion in the calorimeter provides an indirect measurement of the energy content of a food.

The body is not as efficient as a bomb calorimeter and does not completely digest or metabolize the fuels it consumes. The fuels that are not metabolized to energy are stored as either glycogen or body fat. The kilocalorie values obtained from a bomb calo- rimeter must be adapted to reflect the inefficiency of the body. For example, the heat of combustion of protein in meat is approximately 5.65 kilocalories per gram. However, because protein is only 97 percent digested and absorbed, the net kilocalories are actually 4.27 kilocalories per gram.1 These corrected energy values are called physiological fuel values and reflect the kilocalories actually transformed into energy in the body. These are the energy values presented in food composition tables and databases.

Because bomb calorimeters are available only in laboratories, most individuals who want to estimate energy intake use nutrition analysis software or food composition tables to track and add up the kilocalories contained in meals. These resources provide the kilocalorie content of a given food as calculated by multiplying the grams of each energy nutrient in the food by the kilocalories per gram (see the Calculation Corner).

physiological fuel values Real energy value of foods that are digested and absorbed; adjusted from the results of bomb calorimetry because of the inefficiency of the body.

Calculation Corner

Calculating the Energy Content of a Meal Calculate the total energy content of this breakfast meal using the fuel values of 4 kilocalories per gram for carbohydrates and protein and 9 kilocalories per gram for fat.

Food Carbohydrate (g) Protein (g) Fat (g) Kilocalories 1⁄2 cup cooked oatmeal 12 3 0 =                    1⁄2 cup nonfat milk 6 4 0 =                    1⁄2 cup orange juice 12 0 0 =                   

2 slices whole-wheat toast

30 6 2 =                   

1 Tbsp margarine 0 0 10 =                   

8 fl oz coffee 0 0 0 =                   

Total kilocalories =                   

(a) Complete the table by calculating the total kilocalories for each food. Multiply the fuel value of each macronutrient by the number of grams found in each food. For example, 1⁄2 cup of cooked oatmeal would be calculated as follows:

Total kcal = (12 g carbohydrate * 4 kcal/g) + (3 g protein * 4 kcal/g) + (0 g fat * 9 kcal/g)

Total kcal = 60 kcal

(b) After you have calculated the total kilocalories for each food, add the kilocalories for each food together to determine the total kilocalories for the meal.

C

How Is Total Daily Energy Expenditure Calculated? 511

Body Processes and Physical Activity Result in Energy Out The other side of the energy equation is the expenditure of energy. Body processes, from digestion to respiration to circulation, expend energy, as does physical activity, from texting a friend to running up a flight of stairs. Obviously, then, each individual varies in the energy he or she expends throughout the day. Knowing your average daily energy expenditure is essential if you want to either stay in energy balance to maintain your body weight or create an energy imbalance to gain or lose weight. We explain how to estimate your total daily energy expenditure next.

LO 14.1: THE TAKE-HOME MESSAGE Energy balance is the relationship between energy intake and energy expenditure. In positive energy balance, more kilo- calories are consumed than are expended, resulting in weight gain. In negative energy balance, more kilocalories are expended than are consumed, result- ing in weight loss. The kilocalories in foods and beverages provide energy in, whereas basic body processes and physical activity account for energy out.

How Is Total Daily Energy Expenditure Calculated? LO 14.2 Discuss the factors that contribute to total daily energy expenditure,

including basal metabolism, the thermic effect of food, and the thermic effect of exercise.

Several components contribute to our total daily energy expenditure (TDEE); that is, the total kilocalories needed to keep the body functioning and fuel physical activity (Figure 14.3).

Basal Metabolism Contributes to TDEE The energy needed to fuel the body’s vital functions, such as pumping blood, expanding the lungs, and brain function, is known as its basal metabolism and is expressed as a basal metabolic rate (BMR). This is the amount of energy spent to meet the body’s basic physiological needs when it’s at physical, emotional, and digestive rest, but not asleep—in other words, the minimum amount of energy needed to keep your awake, resting body alive. If you sit on the couch to watch television, you aren’t engaged in any physical activity but your cells are still active and require energy for basic functions.

The BMR determines approximately 50–70 percent of your total daily energy use (see Figure 14.3). Your lean body mass (LBM) is the factor that most affects your BMR. Lean body mass is defined as the muscle, bone, and other nonfat tissue that makes up your body weight. Because lean body mass is more active tissue than body fat, it burns kilocalories at a higher rate than stored fat, even at rest. Thus, the more lean body mass you have, the greater your BMR—about 70 percent of your BMR is attributable to the metabolic activity of your LBM. Additional factors such as age, gender, body size, genes, ethnicity, emotional and physical stress, thyroid hormone levels, nutritional state, and envi- ronmental temperature, as well as caffeine and nicotine intake, affect BMR. Table 14.1 explains each of these factors.

BMR, which is determined by an indirect measurement of the amount of oxygen consumed, is measured when a person is awake and cellular activity is the lowest. To get an accurate BMR measurement, your sympathetic nervous system cannot be stimulated. This is the reason a person’s BMR is usually measured in a laboratory setting in the morning while the person lies motionless in a controlled (no shivering or sweating) environment

total daily energy expenditure (TDEE) Total kilocalories needed to meet daily energy requirements.

basal metabolism Amount of energy expended by the body to meet its basic physiological needs, including muscle tone and heart and brain function.

basal metabolic rate (BMR) Measure of basal metabolism taken when the body is at rest in a warm, quiet environment after a 12-hour fast; expressed as kilocalories per kilogram of body weight per hour.

lean body mass (LBM) Total body weight minus the fat mass; consists of water, bones, vital organs, and muscle; metabolically active tissue in the body.

▲ Figure 14.3 Requirements for the Total Daily Energy Expenditure The amount of total energy expended during a 24-hour period is composed of an indi- vidual’s basal metabolism, the thermic effect of exercise or physical activity, which includes adaptive thermogenesis and nonexercise activity thermogenesis, and the thermic effect of foods. A sedentary individual will expend a larger percentage of energy from basal metabolism compared with an active person who would have a greater need for energy to fuel physical activity.

Basal metabolism 50–70%

TEF 10%

TEE (includes adaptive thermogenesis and

NEAT) ~20–35%

Total Daily Energy Expenditure (TDEE)

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after a 12-hour overnight fast. Neither the digestion of food nor physical activity (which both require energy) is factored into the BMR.

Because such precise circumstances are needed to measure BMR, it is a challenge to obtain. For this reason, the resting metabolic rate (RMR) is often used instead. The RMR is the amount of energy used by the body, measured when the person is lying calmly after only a 3- to 4-hour fasting period. The RMR is about 6 percent higher than the BMR, as it reflects increases in energy expenditure related to any recent food intake or physical activity.

The Thermic Effect of Food Contributes to TDEE The digestive system requires kilocalories to digest and absorb the foods you eat, and the amount of energy required for this is called the thermic effect of food (TEF). The body uses energy to process the fuels and extract kilocalories during catabolism. Immediately after eating and for several hours after a meal, energy expenditure increases to provide ATP for chewing, peristalsis, digestion, absorption, and transport of nutrients. Approxi- mately 10 percent of the kilocalories in food consumed is used for TEF. In other words, about 10 kilocalories in a 100-kilocalorie cookie are used to process the cookie. Likewise

resting metabolic rate (RMR) Measure of the amount of energy expended by the body at rest and after approximately a 3- to 4-hour fasting period; about 6 percent higher than BMR.

thermic effect of food (TEF) Amount of energy expended by the body to digest, absorb, transport, metabolize, and store energy-yielding nutrients from foods.

Factor Explanation

Lean body mass Lean body mass, which is mostly muscle mass, is more metabolically active than fat tissue, so more kilocalories are needed to maintain it. Athletes who have a large percentage of lean body mass due to their increased muscle mass have a higher BMR than individuals who aren’t athletic.

Age For adults, BMR declines about 1–2 percent per decade after the early adult years but it increases by 15 percent during pregnancy. For children, BMR increases during times of rapid growth such as infancy and adolescence.

Gender Women have less lean body mass, and typically have a higher percentage of body fat than men. This results in women having a BMR up to 10 percent lower than men’s. Women also tend to have a smaller body size.

Body size Taller individuals have a higher BMR due to increased surface area compared with shorter individuals. More surface area means more heat lost from the body, which causes the metabolism rate to increase to maintain the body’s temperature.

Genes Research suggests that genes may affect BMR, as individuals within families have similar metabolic rates.

Race African Americans have BMRs that are about 10 percent lower than those of Caucasians.

Stress Hormones such as epinephrine, which are released during emotional stress, increase BMR. Physiological stress on the body caused by injury, fever, burns, and infections also causes the release of hormones that raise BMR. Heat loss from the body through wounds, as well as the response of the immune system during infection, increase BMR.

Hormones An increase in thyroid hormone increases BMR, whereas too little of this hormone lowers BMR. Hormone fluctuations during a woman’s menstrual cycle lower BMR during the phase before ovulation.

Starvation Starvation and fasting for more than about 48 hours lower BMR.

Environmental temperature Being very cold or very hot can increase BMR. The change is minimal if clothing or air temperature are adjusted.

Caffeine Caffeine can raise BMR, but only slightly when consumed regularly in moderate amounts.

Drugs Nicotine may increase BMR.* Stimulant drugs such as amphetamine and ephedrine increase BMR.

*Note: Smoking is not a weight-management strategy. Some people may think that replacing snacks with cigarettes helps them stay slim, but the health risks associated with smoking, such as lung cancer, heart disease, and stroke, make it a foolish habit. Anyone concerned about weight gain when quitting smoking can minimize the chances of this with exercise.

Source: Data from Food and Nutrition Board, National Institute of Medicine, Dietary Reference Intakes: The Essential Guide to Nutrient Requirements (Washington, DC: National Academies Press, 2006).

TABLE 14.1 Factors That Affect Basal Metabolism

How Is Total Daily Energy Expenditure Calculated? 513

due to TEF, the gross kilocalories found in a food are slightly more than the net amount available for energy expenditures.

The type of nutrients consumed influences the TEF. For instance, a meal high in protein has the highest thermic effect (approximately 20–30 percent), probably because of the synthesis of body proteins after a protein meal. Carbohydrates have a greater TEF (5–10 percent) than fat (0–3 percent), most likely due to the energy cost to convert glu- cose into glycogen. The energy cost of converting fat into stored triglycerides is minimal. Other factors that influence the TEF, such as composition of a meal, alcohol intake, age, and athletic training status, are presented in Table 14.2. A trained athlete appears to be able to digest and absorb food using fewer kilocalories than the untrained.2 An obese individual may also have a reduced TEF. The reason for the decrease in TEF in obesity may be due to insulin insensitivity.3 Note that the number of kilocalories used for TEF is small compared with the number expended by BMR and physical activity.

The Thermic Effect of Exercise Contributes to TDEE Energy can also be expended by producing heat (thermogenesis). Adaptive thermogenesis is the term used for the processes by which the body regulates heat production. It is influenced by environmental changes such as stress, temperature, or diet, which result in a change in metabolism. Shivering when the temperature drops is an example of adaptive thermogenesis.

Experts are still not sure how adaptive thermogenesis relates to total daily energy expenditure. A reduced ability to produce heat from food energy rather than store the kilocalories in fat tissue may be partly responsible for greater weight gain in overweight individuals versus their lighter peers.4 Some researchers believe adaptive thermogenesis explains why two people can have the same diet and exercise patterns but have completely different body compositions.5

Researchers do know, however, that physical activity is thermogenic. In fact, the heat produced by contracting muscle during physical activity or exercise can contribute signifi- cantly to the amount of energy expended each day. Walking across campus, vacuuming your home, or pulling weeds in the garden are all activities that require energy above the minimum needed for BMR. This expenditure of kilocalories is referred to as the ther- mic effect of exercise (TEE). The number of kilocalories you need each day for TEE

thermogenesis Generation of heat from the basal metabolism, digestion of food, and all forms of physical activity.

thermic effect of exercise (TEE) Increase in muscle contraction that occurs during physical activity, which produces heat and contributes to the total daily energy expenditure.

The process of digesting and absorbing foods requires energy called the thermic effect of food.

Factor Effects on the Thermic Effect of Food

Type of fuel Fat has the least effect on TEF; protein has the greatest effect.

Meal composition Consuming all three macronutrients together produces a lower TEF than would be produced by protein or carbohydrates separately.

Fiber content A high-fiber meal produces a lower TEF.

Age TEF declines as we age.

Environmental temperature

Consuming a meal in a cold environment increases TEF.

Alcohol Alcohol consumption increases TEF but reduces TEF if alcohol is consumed in a cold environment.

Intense exercise TEF is higher following intense exercise.

Training status Individuals who are trained athletes have a lower TEF than untrained individuals.

Obesity Obese individuals have a lower TEF than normal-weight individuals.

Source: Data from J. Kang, Bioenergetics Primer for Exercise Science (Champaign, IL: Human Kinetics, 2008).

TABLE 14.2 Factors That Influence the Thermic Effect of Food

514 Chapter 14 | Energy Balance and Body Composition

depends on the activity itself, the amount of time you perform the activity, and how much you weigh. For instance, if two males run together at the same pace for an hour, but one male weighs 10 kilograms more than the other, the heavier male will burn 496 kilocalories compared with 400 kilocalories for his lighter running partner.

The kilocalories expended for TEE for sedentary people is less than half of their BMR. For very physically active individuals who have a greater muscle mass, TEE can be as much as double their BMR. In short, the more physical activity people incorporate into their daily routine, the more kilo- calories they need to consume to maintain energy balance. For example, two females who weigh the same and are similar in age both have a BMR of 1,200 kilocalories. One female is sedentary and her TEE is only 600 kilocalo- ries, while the second female has a much higher TEE of 2,000 kilocalories because of her physically active lifestyle. Based on her TEE, the sedentary female can only consume 1,800 kilocalories per day (BMR + TEE) to maintain energy balance and not gain weight. In contrast, because of her

higher TEE, the physically active female must eat 3,200 kilocalories per day to meet her energy requirements and not lose weight.

The amount of energy expended during physical activity goes beyond the activity itself. Exercise causes a small increase in energy expenditure for some time after the activity has stopped because of the recovery and adaptation the body undergoes following the exercise.6

In addition to the energy required to walk, jog, or lift weights, TEE also includes the cost of energy to maintain posture and body position, and for fidgeting and other activities we don’t normally consider exercise. This form of energy expenditure is called nonexercise activity thermogenesis (NEAT). NEAT may play a key role in energy bal- ance. Adults who fidget or are hyperactive tend to burn more kilocalories than people who do not. While sitting in front of a computer all day does expend kilocalories, the amount is minimal.7 Read the nearby Examining the Evidence box to learn more on the influence of NEAT on energy expenditure.

Figure 14.4 summarizes the factors on both sides of the energy balance equation that contribute to your total daily energy expenditure.

nonexercise activity thermogenesis (NEAT) Energy expended for all activities not related to sleeping, eating, or exercise, including fidgeting, performing work-related activities, and playing.

Once you crawl out of bed in the morning, the kilocalories you expend to stretch, take a shower, and get dressed are classified as TEE.

▲ Figure 14.4 The Factors Involved in Energy Balance Basal metabolism, the thermic effect of food, and the thermic effect of exercise account for the energy-out side of the energy balance equation. The protein, carbohydrate, fat, and alcohol found in foods and beverages contribute to energy intake.

Carbohydrates

Fats

Proteins

Basal metabolism

Thermic effect of exercise (TEE; includes adaptive thermogenesis and NEAT)

Thermic effect of food (TEF)

Alcohol

Energy in Energy out

What Is NEAT About Fidgeting? 515

EXAMINING THE

EVIDENCE

Fidgeting is one aspect of the energy expenditure referred to as NEAT, or nonexercise activity thermogenesis.1 The term NEAT, coined by cardiologist Dr. James A. Levine, is a component of TEE that refers to the energy we expend for everything we do while awake except eat- ing or participating in structured exercise such as jogging, aerobics, or power walk- ing. NEAT includes walking to work, danc- ing, gardening, and, yes, even fidgeting.

As a nation, the less often we move, the more obese we become.2 Research has reported a strong cor- relation between a drop in NEAT and an increase in weight gain, specifically body fat.3 Studies report that lean peo- ple who are sedentary stand and move 152 minutes longer per day than obese individuals do. And obese subjects sit 164 minutes per day (over 2.5 hours) more than lean subjects. In other words, people who are classified as obese have low NEAT.4 Sitting, it would seem, increases your risk of obesity and all of the health risks associated with excess weight.

The number of kilocalories burned by NEAT activities can vary substan- tially between individuals. Levine and colleagues report that NEAT can vary by almost 2,000 kilocalories per day.5 What accounts for these large differ- ences in daily energy expenditure? Let’s examine the evidence.

Your Occupation Impacts NEAT The advancement of technology has reduced NEAT by limiting the physi- cal activity of jobs in the workplace. According to current research, working in a sedentary occupation is the main factor contributing to lower NEAT.6 Among workers, men with sedentary jobs (secretaries, motor vehicle opera- tors) were 22 percent less active and women were 30 percent less active than those with more active profes- sions, such as farm or construction workers.7 If you compare this to steps taken per day, a desk-bound man or woman takes only 5,000–6,000 steps a day. That compares with about

18,000 steps a day for the average man and 14,000 for the average woman in an Amish farming community.8

In controlled stud- ies of sedentary adults, changes in the work environ- ment that encourage NEAT, such as fidg- eting and standing, have been shown to reduce weight gain. For example, standing rather than sitting is an example of pas- sive work that burns more kilocalories. Figure 1 illustrates the differences of energy expenditure in standing versus sit- ting during work. For those who find it dif- ficult to stand during the workday, sitting on a therapy ball, which requires the individual to contract core muscles, may be another passive means to increase energy expenditure.9 In fact, standing still for hours is not recommended. The important concept is to mix both sitting and standing to avoid injury and burn more kilocalories.10

Research is cur- rently being con- ducted in a variety of office settings on the feasibility of using walking stations in the workplace and the impact these stations may have on body composition, cognitive

What Is NEAT About Fidgeting?

▲ Figure 1 Energy expenditure in males and females expressed as kilocalories per hour during rest, office chair, therapy ball, and standing pos- tures. Data are mean { S.E.; p 6 0.05 for means with the same letter. Based on: E. A. Beers, J. N. Roemmich, L. H. Epstein, and P. J. Horvath. 2008. Increasing Passive Energy Expenditure during Clerical Work. European Journal of Applied Physiology 103:353–360. Copyright © by Springer. Reprinted with permission of Springer Science + Business Media.

a

b

a

b

a

b

0 20 40 60 80 100 Energy expenditure (kcal/hr)

Women

Men

Women

Men

Women

Men

Women

MenR es

t O

ffi ce

c ha

ir Th

er ap

y ba

ll S

ta nd

+ –

Walking slowly at the rate of about 1 mile per hour while working at your desk increases energy expenditure by about 200 kilocalories per hour compared with sitting at your desk.

516 Chapter 14 | Energy Balance and Body Composition

and Obesity and Diabetes in High, Middle, and Low Income Countries. Canadian Medical Asso- ciation Journal. doi: 10.1503/cmaj.131090.

3. Müller, M. J., and A. Bosy-Westphal. 2013. Adaptive Thermogenesis with Weight Loss in Humans. Obesity 21(2):218–228. doi: 10.1002/oby.22027.

4. Gupta, N., D. M. Hallman, et al. 2016. Are Tem- poral Patterns of Sitting Associated with Obesity Among Blue-Collar Workers?: A Cross Sectional Study Using Accelerometers. BMC Public Health 16:148. doi: 10.1186/s12889-016-2803-9.

5. Levine, J. A., W. M. W. Vander, et al. 2006. Non-Exercise Activity Thermogenesis: The Crouching Tiger Hidden Dragon of Societal Weight Gain. Arteriosclerosis, Thrombosis, and Vascular Biolog y 26:729–736.

6. Villablanca, P. A., J. R. Alegria, et al. 2015. Nonexercise Activity Thermogenesis in Obesity Management. Mayo Clinic Proceedings 90:509–519.

7. Aittasalo, M., M. Livson, et al. 2017. Moving to Business – Changes in Physical Activ- ity and Sedentary Behavior after Multilevel Intervention in Small and Medium-Size Workplaces. BMC Public Health 17:319. doi: 10.1186/s12889-017-4229-4.

8. Hairston, K. G., J. L. Ducharme, et al. 2013. Comparison of BMI and Physical Activity Between Old Order Amish Children and Non- Amish Children. Diabetes Care 36(4):873–878. doi: 10.2337/dc12-0934.

9. Pederson, S. J., et al. 2013. An E-Health Intervention Designed to Increase Workday Energy Expenditure by Reducing Prolonged Occupational Sitting Habits. Work. doi: 10.3233/WOR-131644.

10. Van Nassau, F., J. Y. Chau, et al. 2015. Valid- ity and Responsiveness of Four Measures of Occupational Sitting and Standing. International Journal of Behavioral Nutrition and Physical Activity 12:144. doi: 10.1186/ s12966-015-0306-1

11. Lear. 2014. The Association between Own- ership of Common Household Devices and Obesity and Diabetes in High, Middle, and Low Income Countries.

12. ChooseMyPlate. 2015. How Many Calories Does Physical Activity Use? Available at www .choosemyplate.gov. Accessed March 2017.

13. Villablanca, P. A., J. R. Alegria, et al. 2015. Nonexercise Activity Thermogenesis in Obesity Management.

function, and job productivity. The use of walking desks should increase NEAT energy expenditure and may improve overall health in the workplace.

Leisure Time Affects NEAT Labor-saving devices and technol- ogy make it possible to squelch much leisure-time NEAT through the use of riding lawnmowers, electronically programmed vacuum cleaners, bread machines, microwave ovens, elec- tric hammers, and handheld video games.11 Consider your leisure-time hours after work or school and on the weekends. Do you surf the Internet or watch television for hours until bed- time, just moving the mouse or using the remote control? If this were your routine after work, the average energy expenditure for that sedentary activ- ity would be about 70 kilocalories per hour.12 What if you cleaned the house, walked your dog after dinner, or worked in the garden as an alternative? Instead of 70 kilocalories per hour, you could burn 200–400 kilocalories per hour. This change in NEAT could potentially increase the amount of energy you burn by more than 800 kilocalories per day.

NEAT Changes with Food Intake Research suggests that when you eat too much, NEAT increases, and when you eat too little, NEAT decreases. This was illustrated in a study that overfed nonobese subjects 1,000 kilocalories per day for 8 weeks. As expected, the subjects gained between 1.4 kilograms and 7.2 kilograms of weight. What was unexpected was that there was also an increase in NEAT, including changes in posture, fidgeting, and daily activities. The increase in NEAT seemed to be a factor in those who gained less weight than the others. The researchers concluded that the increase in NEAT helped resist additional weight gain even when subjects overate.13

Move and Walk More to Prevent Obesity Even if you engage in regular struc- tured exercise, your overall daily energy expenditure may be relatively low if you spend the rest of your time sitting. The

FITNESS TIPS

Increase Your NEAT Find a friend at work to walk with at lunch.

Stand or pace while talking on the telephone.

Put on your headset and listen to your favorite music while you walk during your morning break.

When you watch television, stretch your shoulders, back, and legs.

Fold laundry while watching your favorite TV show.

Take the stairs instead of riding the elevator or escalator.

If you drive to work or school, park farther from the building.

Buy a pedometer to measure your steps; aim for 10,000 per day.

secret to increasing your NEAT and burning more kilocalories during the day, especially during work hours, is to get up out of the chair and move more. Find ways to work simple movements into your day—tap your feet, pace while you talk on the phone, stand while you read, get up and walk to a coworker’s desk instead of emailing. Any additional NEAT activities will help minimize the potential health risks of a chair-sitting lifestyle. See the Fitness Tips for helpful suggestions.

References 1. Villablanca, P. A., J. R. Alegria, et al.

2015. Nonexercise Activity Thermogen- esis in Obesity Management. Mayo Clinic Proceedings 90(4):509–519. doi: 10.1016/j. mayocp.2015.02.001.

2. Lear, S. A., et al. 2014. The Association between Ownership of Common Household Devices

LO 14.2: THE TAKE-HOME MESSAGE About 50–70 percent of total daily energy expenditure (TDEE) is attributable to basal metabolic rate (BMR), the amount of energy spent to meet the body’s basic physiological needs when it is at rest. Lean body mass accounts for about 70 percent of BMR. In addition to BMR, TDEE includes the thermic effect of food (TEF), or the energy spent to digest and absorb nutrients from food; adaptive thermogenesis, the pro- cesses by which the body regulates heat production; and the thermic effect of exercise (TEE), which includes the energy spent on physical activities and nonexercise activity thermogenesis (NEAT).

How Do We Measure Energy Expenditure? 517

How Do We Measure Energy Expenditure? LO 14.3 Explain how energy expenditure is measured and calculate basal

metabolic rate and estimated energy requirement using equations and physical activity factors.

Have you ever wondered how many kilocalories you burn walking to class or washing your car? Or how resting metabolic rate is calculated? Several methods have been developed to measure energy expenditure. Some of these methods require the skills of a trained technician using expensive equipment. Other methods involve simple equations and a calculator.

Direct and Indirect Calorimetry Measure Energy Expenditure An individual’s energy expenditure can be measured by direct or indirect calorimetry. Both methods quantify the amount of energy produced during rest and physical activity.

Direct calorimetry measures the amount of heat the body generates and can be determined using a metabolic chamber in a specialized laboratory. Briefly, a metabolic chamber is an airtight room designed with the comforts an individual would need for normal daily living such as a bed, chair, TV, telephone, treadmill for exercise, and bathroom. The temperature and relative humidity in the room are controlled and the oxygen and carbon dioxide concentrations of the air supply and exhaust are measured for 24 hours. The concept is similar to the bomb calorimeter, but rather than measur- ing the amount of heat generated by burning food, this method measures the change in water temperature caused by heat that dissipates from the body of a person in the chamber. Although this method provides a precise answer to the question of how many kilocalories an individual expends, for most people its use is too expensive and impractical.

The more practical and less expensive approach is to use indirect calorimetry to estimate the amount of energy expended. Indirect measurements sample the amount of oxygen consumed and carbon dioxide produced during exercise and for a specific amount of time. Metabolic calculations can then be done to determine energy expenditure. Figure  14.5 illustrates two examples of indirect calorimetry—at rest and during physical activity. Figure 14.5a illustrates the use of a metabolic cart, which measures the uptake of oxygen and the output of carbon dioxide to determine resting energy expenditure while sitting in a metabolic chamber. Figure 14.5b illus- trates the use of a collection bag, which collects expired carbon dioxide, allowing researchers to calculate oxygen consump- tion and thereby energy expenditure during exercise.

direct calorimetry Direct measurement of the energy expended by the body; obtained by assessing heat loss.

indirect calorimetry Indirect measurement of energy expenditure obtained by measuring the amount of oxygen consumed and carbon dioxide produced.

▲ Figure 14.5 Medical Tools Can Indirectly Measure Energy Expenditure Researchers can use (a) a metabolic cart to measure the amount of oxygen consumed and car- bon dioxide produced at rest or (b) a collection bag to calculate oxygen consumed and carbon dioxide produced during exercise. This information can then be used to indirectly calculate an individual’s energy expenditure.

a Measuring metabolic rate at rest b Measuring metabolic rate during exercise

518 Chapter 14 | Energy Balance and Body Composition

Simple Calculations Are Used to Estimate Energy Expenditure Recall from Chapter 2 that the DRIs include the estimated energy requirement (EER), which is the average kilocalorie intake that is estimated to maintain energy balance. An individual’s EER is based on gender, age, height, body weight, and level of physical activity. The physical activity levels are assigned numerical values from sedentary (1.00) to very active (1.45–1.48), as shown in Table 14.3. The calculation used by the DRI committee to estimate EER is presented in the Calculation Corner.8 You can obtain an even more precise EER by assessing every minute of movement and physical activity that you do throughout the day and, based on this, calculating the energy that you expend.

estimated energy requirement (EER) Average kilocalorie intake that is estimated to maintain energy balance based on a person’s gender, age, height, body weight, and level of physical activity.

Calculation Corner

What’s Your Estimated Energy Requirement (EER)? You can estimate your energy requirement for kilocalories using this two-step calculation:

(1) First, complete the information below. (a) My age is            . (b) My physical activity during the day based on Table 14.3 is            . (c) My weight in pounds is             divided by 2.2 = kilograms. (d) My height in inches is             divided by 39.4 = meters.

(2) Using your answers from each part of step 1, complete the following calculation based on your gender and age.

Males, 19+ years old, use this calculation:

EER = [662 - (9.53 * )] + * [(15.91 * ) + (539.6 * )]

(a) (b) (c) (d)

Females, 19+ years old, use this calculation:

EER = [354 - (6.91 * )] + * [(9.36 * ) + (726 * )]

(a) (b) (c) (d)

(3) Now calculate Will’s EER. Will is 21 years old, weighs 180 pounds, and stands at 5 feet 11 inches tall. He describes his physical activity level as active. What is Will’s estimated energy requirement?

C

Physical Activity Factor for

Physical Activity Level Men Women

Sedentary 1.00 1.00

Low level of activity (walking approximately 2 miles per day at 3 to 4 miles per hour)

1.11 1.12

Active (walking approximately 7 miles per day at 3–4 miles per hour)

1.25 1.27

Very active (walking approximately 17 miles per day at 3–4 miles per hour)

1.45 1.48

Source: Data from Food and Nutrition Board, National Institute of Medicine, Dietary Reference Intakes: The Essential Guide to Nutrient Requirements (Washington, DC: National Academies Press, 2006).

TABLE 14.3 Physical Activity Factors for Men and Women

Go to Mastering Nutrition and complete a Math Video activity similar to the problem in this Calculation Corner.

What Is Body Composition and How Is It Assessed? 519

Another calculation often used is the Harris-Benedict equation, which also calculates RMR based on gender, age, height, and weight and applies an activity factor to determine total daily energy expenditure. The drawback to this equation is that it does not include lean body mass, so it may not be accurate for individuals who are very muscular (for whom it underestimates kilocalorie needs) or who are very fat (for whom it overestimates kilo- calorie needs). In those circumstances, other calculations may be used in clinical settings.

Want to increase your energy expenditure? Check out the nearby Fitness Tips.

FITNESS TIPS

Achieve Energy Balance Track the number of kilocalories you consume in one day, and compare it with the estimated number of kilocalo- ries you expend. Are you most often in positive, or negative, energy balance?

Take steps to increase muscle mass, such as by weight training. This helps increase your metabolic rate.

Keep a diary to calculate how much energy you expend each day doing normal, everyday tasks.

Identify your favorite exercise that you can engage in at least 30 minutes a day most days of the week to avoid too much sedentary time.

LO 14.3: THE TAKE-HOME MESSAGE Energy expenditure can be measured by direct calorimetry using a metabolic chamber or by indirect calorimetry using a metabolic cart or collection bag. Simple calculations can also be used to estimate energy expenditure using age, height, weight, and level of physical activity.

What Is Body Composition and How Is It Assessed? LO 14.4 Define the term body composition, and explain the methods used to

assess lean body mass and body fat.

Body tissues include bone, skin, muscle, fat, organs, and blood, which are made up of the same basic nutrients: water, protein, minerals, and fat. The ratio of fat tissue to lean body mass is called body composition. This ratio, stated as percent body fat, is particularly important for the sake of measuring health risks associated with too much body fat.

Most Body Fat Is Stored in Adipose Tissue Two types of fat make up total body fat: essential fat, which includes the fat found in the bone marrow, heart, lungs, liver, spleen, kidneys, intestines, muscles, and central nervous system, and stored fat, found in adipocytes. Essential fat is just that—essential for the body to function. Women have four times (12 percent) more essential fat than men (3 percent) because of the fat deposits in breast tissue and surrounding the uterus.

Every cell contains some fat, but most body fat is the stored fat found in adipocytes, either as subcutaneous fat under the skin or as visceral fat around the internal organs. Subcutaneous and visceral fat insulate the body from cold temperatures and help protect and cushion the internal organs (Figure 14.6). Men and women store subcutaneous fat slightly differently, with men more likely to accumulate it in the belly, hips, and thighs, and women more apt to store it in the breasts, neck, and upper arms, as well as in the hips and thighs.

Adipocytes release fat to be used as fuel when the body is in negative energy balance. An adipocyte shrinks as more fat is hydrolyzed from storage and overall body weight is lost. When the body is in positive energy balance, fat accumulates in the adipocytes, which expand in size, and weight gain occurs.

Adipose tissue is described as white fat because of its creamy white appearance. Another type of adipose tissue, called brown adipose tissue (BAT), is made up of specialized fat cells that contain more mitochondria and are rich in blood (Figure 14.7). While white adipose tissue is used as a storage depot for excess kilocalories, the function of BAT is to generate heat. Found primarily in infants, BAT protects infants from heat loss and cold. Recent research suggests that adults, especially older adults, have more BAT than once thought. Studies have shown that the more BAT an adult has, the lower their body mass index, suggesting that this active tissue plays an important role in adult metabolism.9 This may be due to the fact that brown adipose tissue converts kilocalories into heat rather than storing them.

body composition Ratio of fat to lean tissue (muscle, bone, and organs) in the body; usually expressed as percent body fat.

essential fat Component of body fat that is necessary for health and normal body func- tions; includes the fat stored in the bone marrow, heart, lungs, liver, spleen, kidneys, intestines, muscles, and the lipid-rich tissues of the central nervous system.

subcutaneous fat Fat located under the skin and between the muscles.

visceral fat Body fat associated with the internal organs and stored in the abdominal area.

brown adipose tissue (BAT) Type of adipose tissue, found primarily in infants, that produces body heat; gets its name from the large num- ber of mitochondria and capillaries responsible for the brown color.

520 Chapter 14 | Energy Balance and Body Composition

Body Fat Level and Distribution Affect Health Carrying either too much or too little body fat can affect body functions and impair health. Everyone needs to have a certain amount of body fat to meet basic needs, but excess amounts of body fat can impair overall health. For this reason, specific body composition standards have been developed over the years from a variety of research studies to help individuals avoid health risks (Table 14.4). These body fat ranges, which can be measured using a variety of indirect methods (discussed shortly), are based on epidemiological studies of the general population of Americans.

How much fat you carry isn’t the only determinant of health risk—where you carry it also matters. Storing excess fat around the waist versus carrying it around the hips and thighs has been shown to increase the risk of heart disease, diabetes, and hypertension.10

Central (or android) obesity occurs when excess visceral and subcutaneous fat is stored in the abdomen (Figure 14.8). This is sometimes referred to as an “apple-shaped” fat distribution pattern and is more common in men than in women. Gynoid obesity is due to excess fat stored in the lower part of the body around the thighs and buttocks. This “pear-shaped” fat distribution pattern is more frequently found in women than in men.

Subcutaneous fat

Liver Stomach Abdominal muscle

Loops of intestine

Visceral fat

Subcutaneous fat

Liver Stomach Abdominal muscle

Loops of intestine

Visceral fat

▲ Figure 14.6 Visceral and Subcutaneous Fat Storage in the Body Visceral fat stored around the abdominal organs is more likely to lead to health problems than is subcutaneous fat sandwiched between the muscle and skin.

▲ Figure 14.7 White Adipocyte and Brown Adipocyte Brown adipose tissue has significantly more mitochondria and less stored triglyceride than white adipose tissue.

Nucleus

Mitochondrion

Triglycerides

White adipocyte

Brown adipocyte Men Women

Essential fat Desirable fatness for good health Overfat

3 percent of total body fat 10–20 percent body fat

More than 25 percent body fat

12 percent of total body fat 16–26 percent body fat

More than 30 percent body fat

Source: Data from W. D. McArdle, F. I. Katch, and V. L. Katch, Sports and Exercise Nutrition, 4th ed. (Baltimore: Lippincott Williams & Wilkins, 2012).

TABLE 14.4 Body Composition Reference Standards for Adult Men and Women

What Is Body Composition and How Is It Assessed? 521

Fatty acids released from visceral fat located near the liver are believed to travel to the liver and contribute to hyperlipidemia. Visceral fat also contributes to insulin resistance, high levels of blood triglyceride, low levels of the good HDL cholesterol, and high levels of LDL cholesterol in the blood, which all increase the risk of heart disease and diabetes. Insulin resistance also increases the risk for hypertension. Men, postmeno- pausal women, and obese people tend to have more visceral fat than young adults and lean individuals.

Body Composition Is Assessed Indirectly There are several indirect measurements used to estimate the percentage of body fat and lean body mass in the body. The most popular indirect techniques are found in laboratory settings and include hydrostatic weighing, air displacement, dual-energy X-ray absorptiometry (DEXA), bioelectrical impedance, and skinfold measurement (Table 14.5).

Percent Body Fat Because fat mass has a lower density than either muscles or bones, it is possible to estimate body fat percentage from body volume. Hydrostatic weighing and air-displacement plethysmography are two methods that use body volume to measure percent body fat. Hydrostatic weighing is based on the principle that an object immersed in water is buoyed up by a force equal to the weight of the fluid displaced by the object. In other words, if the density of an object is greater than the density of water, the object sinks. If the density of the object is less than water, the object floats. We can use this principle to determine body composition by measuring the difference in body weight in air compared with under water. With a 2–3 percent margin of error, hydrostatic weighing is considered one of the most accurate assessment tools. The BodPod, an air displacement plethysmography device that measures air rather than water displacement, is similarly accurate within 3 percent. Both hydrostatic weighing and the BodPod have pros and cons. While both are accurate, hydrostatic weighing takes longer; some people find it difficult to be submersed under water; and the equipment is usually only found in research facilities. The BodPod, on the other hand, is faster and it only requires you to sit quietly in a chamber. See the Calculation Corner for the equation used to determine body composition from either of these body volume methods.

hydrostatic weighing Method used to assess body volume by underwater weighing.

air-displacement plethysmography Proce- dure used to estimate body volume based on the amount of air displaced.

central or android obesity Excess storage of visceral fat in the abdominal area, indicated by a waist circumference greater than 40 inches in males and 35 inches in females; cen- tral obesity increases the risk of heart disease, diabetes, and hypertension.

gynoid obesity Excessive storage of body fat in the thighs and hips of the lower body.

▲ Figure 14.8 Android and Gynoid Fat Distribution Patterns Men and women store fat differently. Men tend to store it in the upper body including the abdomen, chest, neck, and back—often referred to as “apple-shaped” fat distribu- tion—whereas women tend to store it below the waist including the buttocks, hips, and thighs for more of a “pear-shaped” appearance.

Above waist

Below waist

Gynoid “pear- shaped” fat distribution

Android “apple- shaped” fat distribution

Calculation Corner

Body Volume and Density The body volume determined by either hydrostatic weighing or air displacement is mathematically converted to density and then to percentage of body fat using this equation:

Body density = body weight (kg)/body volume (L) Percentage of body fat = (495/body density) - 450

Example: The body volume of an 83-kilogram male (182.6 pounds) was determined from hydro- static weighing to be 79.4 L. Dividing body weight by body volume yields a body density of 1.0453. Body density can then be used to determine percent body fat as follows:

(495/1.0453) - 450 = 23.5 percent body fat

C

522 Chapter 14 | Energy Balance and Body Composition

Cost: $$ Accuracy: 2–3% margin of error

Cost: $$$ Accuracy: 2–3% margin of error

Cost: $$$ Accuracy: 1–4% margin of error

Cost: $ Accuracy: 3–4% margin of error

Cost: $ Accuracy: 3–4% margin of error

$, very affordable; $$, less affordable;

$$$, expensive

TABLE 14.5 Ways to Measure Percentage of Body Fat

▲ Hydrostatic Weighing How It Is Done: To determine the den- sity of the body, a person is weighed both on land and suspended in a water tank. Fat is less dense and weighs less than muscle mass and this is reflected in the person’s weight in the water. The difference of a person’s weight in water and on land is then used to calculate the percentage of body fat.

▲ Bioelectrical Impedance (BIA) How It Is Done: An electric current flows through the body and its resis- tance is measured. Lean tissue is highly conductive and less resistant than fat mass. Based on the current flow, the volume of lean tissue can be estimated. From this information, the percentage of body fat can be determined.

▶ Air Displacement Plethysmography Using a BodPod How It Is Done: A person’s body volume is determined by measuring air displacement. The person sits in a special chamber (called the BodPod) and the air displacement in the chamber is measured. From this measure- ment, the percentage of body fat can be estimated.

◀ Dual-Energy X-Ray Absorptiometry (DEXA) How It Is Done: Beams of X-ray energy from two different sources are used to mea- sure bone, fat, and lean tissue. The different types of tissue that the beams pass through absorb different amounts of energy. The percentage of body fat can be determined from the difference in the readings.

▶ Skinfold Thickness Measurements How It Is Done: Calipers are used to measure the thickness of fat that is located just under the skin in the arm, in the back, on the upper thigh, and in the waist area. From these measurements, percent body fat can be determined.

How Do We Estimate a Healthy Body Weight? 523

Dual-energy X-ray absorptiometry (DEXA) is the most accurate method of deter- mining body composition; its margin of error is only 1–4 percent. DEXA is a noninvasive method that can estimate three body compartments: fat mass, lean body mass, and bone mass. This noninvasive method uses two low-energy X-ray beams: one detects all tissues including fat mass and bone mass and the other detects only lean body mass. The com- puter then calculates the difference between lean body mass and fat mass to determine the percentage of body fat.

Bioelectrical impedance analysis (BIA) measures the resistance to a low-energy current as it travels through muscle and body fat. The current travels more quickly through lean tissue, which is high in body water and electrolytes, than through fat tissue. The resistance of the fat tissue is used to calculate body composition. BIA is not as accurate as body density tests and can be affected by age, hydration status, and consuming food and alcohol prior to the test.

Anthropometric (relating to body measurement) techniques are the simplest methods available and involve using a skinfold caliper to measure fat in various body locations. The metal calipers are used to pinch the subcutaneous fat at selected sites on the body. A trained technician grasps the skin and fat between the thumb and forefinger and pulls it gently away from the muscle. The caliper exerts a constant pressure while measuring the skinfold thickness in millimeters. These values are then used to calculate percent body fat. When conducted by a trained technician, skinfold caliper tests are fairly accurate.

Waist Circumference Because abdominal fat can be particularly detrimental to health, measuring a per- son’s waist circumference can quickly reveal whether he or she is at increased risk (Figure 14.9). A woman with a waist measurement of more than 35 inches or a man with a measurement of more than 40 inches is at a higher risk for disease than people with slim- mer middles. Carrying extra fat around the waist can increase health risks even if you are not overweight. In other words, a person who may be at a healthy weight based on their height, but who has excess fat around the middle, is at a higher risk for disease.

dual-energy X-ray absorptiometry (DEXA) Method that uses two low-energy X-rays to measure body density and bone mass.

bioelectrical impedance analysis (BIA) Method used to assess the percentage of body fat by using a low-level electrical cur- rent; body fat resists or impedes the current, whereas water and muscle mass conduct electricity.

skinfold caliper Tool used to measure the thickness of subcutaneous fat.

waist circumference Measurement taken at the top of the iliac crest or hip bone; used to determine the pattern of obesity.

▲ Figure 14.9 Measuring Waist Circumference The waist circumference measurement is taken at the top of the iliac crest (top of the hip bone), as shown by the dashed line.

LO 14.4: THE TAKE-HOME MESSAGE The body is composed of lean and fat tissue. Adipose tissue is classified as essential fat or fat that is stored as either subcutaneous or visceral fat. How much fat a person has and the placement of that fat can increase the risk of heart disease, diabetes, and hypertension, especially if the fat is distributed in the abdomen. Hydrostatic weighing, air displacement plethysmography, dual-energy X-ray absorptiometry (DEXA), bioelectrical impedance analysis (BIA), and skinfold measurements are all tech- niques used to determine body composition. Measuring waist circumference can determine whether an individual has excess abdominal (central) fat, which can increase the risk of several chronic diseases.

How Do We Estimate a Healthy Body Weight? LO 14.5 Explain the methods used to estimate a healthy body weight, and the

link between body weight and mortality.

The terms body weight and body composition are not synonymous. Body weight is defined as total mass expressed in either pounds (lb) or kilograms (kg). As you just learned, body composition is the percentage of body weight that is composed of fat and lean body mass. Even though the terms body weight and body composition do not measure the same component, they are often used interchangeably in the popular media.

524 Chapter 14 | Energy Balance and Body Composition

Two common methods used to help individuals estimate whether their own per- cent body fat falls within a healthy range are height–weight tables and body mass index (BMI). These reference standards are indirect estimates of body composition, and there- fore somewhat imprecise, but they can be used as a rough guide for most people.

Height and Weight Tables Are Problematic Height–weight tables have been used since the 1940s in large-scale studies that were designed to investigate the relationship between body weight and disease. The Metro- politan Life Insurance Company developed the most commonly used height–weight table. The company published the Desirable Weights for Men and Women table in 1959 based on data collected from millions of policyholders. The most recent version of the table was published in 1999 and provides a recommended desirable weight range for a given height based on gender and body frame size.

Several factors make the data used in these tables problematic. For example, the data does not represent the American population as a whole. The tables were originally designed with data from 25- to 59-year-olds, which means they may underrepresent older adults and individuals younger than 25 years of age. The researchers did not standardize the original data. For instance, subjects self-reported their height and weight; the weights were measured at different times of the year; and there was no standard procedure regarding wearing shoes or clothing when taking the height and weight measurements. Lastly, the tables were constructed with the assumption that weight is associated with body fat. Today, mostly insurance companies use height–weight tables to determine mortality rates. Most health experts use body mass index rather than height–weight tables to determine healthy weight.

Body Mass Index Is a Useful Indicator of Healthy Weight for Most People Body mass index (BMI) (Figure 14.10) is a convenient method of calculating body weight in relationship to height, and is a useful screening tool to determine an individual’s risk of disease. It is calculated using either of the following formulas:

BMI = body weight (in kilograms)

height2 (in meters)

BMI = body weight (in pounds) * 703

height2 (in inches)

A BMI of 18.5924.9 kg/m2 is considered a healthy weight based on height. A BMI below 18.5 kg/m2 is considered underweight or having a body weight that is below normal, average, or considered healthy. A BMI between 25 and 29.9 kg/m2 is considered overweight, and a BMI between 30 and 39.9 kg/m2 is considered obese. Severe obesity is a BMI at or above 40. Table 14.6 summarizes the BMI criteria for defining these terms in adults, and Table 14.7 compares three ways to classify obesity specifically.

As the BMI decreases below 18.5, or increases above 25, the risk of premature death increases. That risk is modest for those with a BMI between 25 and 29.9;11 however, obese individuals have a 50–100 percent higher risk of dying prematurely than those at a healthy weight. Again, underweight is also risky. Adults with a BMI below 18.5 have a greater risk of premature death than those with a BMI of 18.5–24.9.12 BMI has been shown to cor- relate with health risks associated with excess body fat, and an equation can be used to estimate body fat percentage from BMI (see the Calculation Corner).

While BMI can be useful in determining disease risks, it is important to note that BMI is not a direct measure of the percentage of body fat, and it doesn’t specify if body weight is predominantly muscle or fat.13 Therefore, athletes and people with a high

body mass index (BMI) Calculation of body weight in relationship to height.

healthy weight Body weight in relationship to height that doesn’t increase the risk of developing any weight-related health problems or diseases. A BMI between 18.5 and 24.9 is considered healthy.

underweight Weighing too little for your height; defined as a BMI less than 18.5.

overweight Body weight that increases risk of developing weight-related health problems; defined as having a BMI between 25 and 29.9.

obese Condition of excess body weight due to an abnormal accumulation of stored body fat; a BMI of 30 or more is considered obese.

severe obesity Defined as a BMI greater than 40 or more than 100 pounds over ideal body weight.

How Do We Estimate a Healthy Body Weight? 525

◀ Figure 14.10 What’s Your BMI? A BMI between 18.5 and 24.9 is considered healthy. A BMI over 25 is considered over- weight, and a BMI over 30 is obese. A BMI under 18.5 is considered underweight, and can also be unhealthy.

6'6"

6'5"

6'4"

6'3" 6'2" 6'1"

6'0" 5'11"

5'10"

5'9" 5'8"

5'7" 5'6"

5'5"

5'4"

5'3"

5'2"

5'1"

5'0" 4'11" 4'10"

50 75 100 125

18.5 25 BMI (Body Mass Index)

30

150

Weight (pounds) †

* The height is without shoes. † The weight is without clothing.

175 200 225

Healthy weight

Overweight

Obese

250 275

H ei

gh t*

Underweight

Classification BMI (kg/m2)

Underweight 6 18.5 Normal weight 18.5–24.9

Overweight 25–29.9 (also defined as being 10–15 pounds above a healthy weight)

Obesity 30–39.9

Severe obesity 7 40

TABLE 14.6 Definitions of Underweight, Overweight, and Obesity in Adults

Obesity Is Classified by . . .

Percent of body fat Women: 7 32, Men: 7 25,

Distribution of body fat Excess subcutaneous and visceral fat stored in the upper body (abdomen and waist); referred to as central or android obesity

• Waist circumference 7 35 inches in women • Waist circumference 7 40 inches in men Excess subcutaneous fat stored in the lower body (hips, buttocks, thighs); referred to as gynoid obesity

• Waist-to-hip ratio 6 0.8 in women • Waist-to-hip ratio 6 0.95 in men

Body mass index (BMI) Women: 7 30 kg/m2

Men: 7 25 kg/m2

Source: Adapted from A. G. Kazaks and J. Stern, Nutrition and Obesity. Assessment, Management, and Prevention (Burlington, MA: Jones & Bartlett Publishing, 2013).

TABLE 14.7 Ways to Classify Obesity in Adults

526 Chapter 14 | Energy Balance and Body Composition

percentage of muscle mass may have a BMI over 25 kg/m2, yet have a low percentage of body fat. Although these individuals are overweight based on their BMI, they are not “overfat” and unhealthy, and their muscular weight doesn’t increase their health

risk. In contrast, an older adult may be in a healthy weight range, but steadily lose weight due to an unbalanced diet or poor health. This chronic weight loss is a sign of loss of muscle mass and the depletion of nutrient stores in the body, which increases health risks even though the BMI seems healthy. Also, because height is factored into the BMI, individuals who are very short—less than 5 feet—may have a high BMI but, similar to athletes, may not be unhealthy.14

Combining indirect measurements is one way to get a better estimate of body composition. For example, a person who has both a BMI greater than 25 and a large waist circumference is considered at a higher risk for health problems than if he or she only had a high BMI but a low waist circumference (Figure 14.11).

Again, a healthy body weight does not increase the risk of pre- mature death or any weight-related health problems or diseases. In contrast, being underweight or overweight increases the risk for premature death and for numerous diseases. The health risks associ- ated with both underweight and overweight are discussed in detail in Chapter 15.

This male gymnast stands 5 feet 5 inches tall and weighs 160 pounds. His BMI of 26.6 would place him in the overweight category without considering his low percentage of body fat.

▲ Figure 14.11 Using BMI and Waist Circumference to Determine Health Risk Considering both BMI and waist circumfer- ence can give you a good idea of total risk levels for several chronic diseases.

Extremely High Risk BMI 40+ and high waist circumference

Very High Risk BMI 30–39.9 and high waist circumference

High Risk BMI 25–29.9 and high waist circumference or BMI 30–34.9 and low waist circumference

Increased Risk BMI 25–29.9 and low waist circumference

Low Risk BMI under 25

Calculation Corner

Converting BMI to Percent Body Fat Now that you have learned how to calculate body mass index (BMI), how does this number correlate to the amount of stored body fat? Researchers have developed equations that show a correlation between BMI and percent body fat in adults.1 The formulas, which are age and gender specific, can yield valid estimates of body fat comparable to those obtained from skinfold thickness measurements or BIA. The prediction equations do, however, overestimate percent body fat in obese individuals. Follow these steps to practice using these prediction equations.

(1) If you are a female, use this formula: 1.2 (BMI) + 0.23 (age(y)) - 5.4 For example, a 21-year-old female with a BMI of 25 would calculate percent body fat as follows:

1.2 (25) + 0.23 (21) - 5.4 = 30 + 4.83 - 5.4 = 29.43 percent body fat

(2) A male would use this formula: 1.2 (BMI) + 0.23 (age(y)) - 16.2 For example, a 31-year-old male with a BMI of 21 would calculate percent body fat as follows:

1.2 (21) + 0.23 (31) - 16.2 = 25.2 + 7.13 - 16.2 = 16.13 percent body fat

Now, using your own BMI, complete the calculation for percent body fat.

Note that these calculations do not consider race/ethnicity. The BMI–body fat relationship varies between different racial/ethnic groups2 and should be used in conjunction with other measurements such as waist circumference and percent body fat to provide a true picture of a healthy body weight.

References 1. P. Deurenbert, J. A. Weststrate, and J. C. Seidell. 1991. Body–Mass Index as a Measure of Body

Fatness: Age- and Sex-Specific Prediction Formulas. British Journal of Nutrition 65:105–114. 2. Balasubramanian, B. A., M. P. Garcia,

D. A. Corley, et al. 2017. Racial/Ethnic Differences in Obesity and Comorbidities Between Safety-Net and Non Safety-Net Inte- grated Health Systems. Medicine 96(11):e6326. doi: 10.1097/MD.0000000000006326.

C

Go to Mastering Nutrition and complete a Math Video activity similar to the problem in this Calculation Corner.

What Is Disordered Eating? 527

LO 14.5: THE TAKE-HOME MESSAGE Height and weight tables and BMI are used to screen for overweight and obesity. Height–weight tables do not nec- essarily indicate a healthy weight for everyone. The body mass index (BMI) is a calculation of the ratio of weight to height and can be used to assess health risks. A BMI less than 18.5 kg/m2 is considered underweight. A BMI of 18.5924.9 kg/m2 is normal weight. A BMI of 25929.9 kg/m2 is overweight. A BMI of 30939.9 kg/m2 is considered obesity, and 40 kg/m2 or above is considered severe obesity. Both underweight and overweight, especially obe- sity, are associated with an increased risk of premature death and numerous health problems.

HEALTHCONNECTION

Eating Disorders Occur in Both Women and Men In the United States, an estimated 30  million people of various genders and ages struggle with eating disorders.15 Adolescent and young adult females in predominantly white upper-middle- and middle-class families are the population

with highest prevalence. However, eating disorders and disordered eating among males, racial and ethnic minorities, and other age groups are increasing.16,17 Any- one can develop an eating disorder.

Societal pressure to be thin and have a “perfect” figure is one factor that likely contributes to disordered eating among girls and women. Images of models and celebri- ties with abnormally low body weights are portrayed as ideal; therefore, many normal- weight females believe that they cannot be beautiful, successful, or happy unless they are thin. Many females will try to achieve a perfect figure at any cost, including plastic surgery, liposuction, and engaging in disor- dered eating behaviors.

The prevalence of eating disorders in males is difficult to assess because many men, as well as women, feel ashamed or embarrassed and may hide their problem. In fact, the prevalence of eating disorders among both males and females is probably higher than reported. Researchers have found that men diagnosed with eating dis- orders have higher rates of other psychiatric illness such as depression and anxiety disor- ders compared with men who do not have eating disorders.18

What Is Disordered Eating? LO 14.6 List the criteria used to

diagnose eating disorders and dis- cuss the shared traits and options for treatment.

Attaining a healthy weight, whether it means gaining or losing a few pounds, is a worthwhile goal that can result in lowered risk of disease and a more productive life. However, patterns of eating that involve severe kilocalorie restriction, binge eating, purging, or other abnormal behaviors can be severely damaging to health. Whereas disordered eating and eating disorders are sometimes thought of as psychological rather than nutrition-related topics, it’s important to be aware of them and rec- ognize their symptoms.

The term disordered eating is used to describe a variety of eating patterns con- sidered abnormal and potentially harmful. Refusing to eat, compulsive eating, binge eat- ing, restrictive eating, vomiting after eating, and abusing diet pills, laxatives, or diuretics are all examples of disordered eating behav- iors. Eating disorders, in contrast, are psy- chiatric disorders diagnosed when a person meets specific criteria that include disordered eating behaviors as well as other factors. It is possible for someone to have disordered eat- ing without having an actual eating disorder.

disordered eating Abnormal and potentially harmful eating behaviors that do not meet spe- cific criteria for a clinical eating disorder.

eating disorders Psychiatric illnesses that involve specific abnormal eating behaviors.

Societal pressure to be thin can cause people to feel fat when they look in the mirror regard- less of their body weight. Dissatisfaction with one’s body can lead to disordered eating behaviors.

528 Chapter 14 | Energy Balance and Body Composition

HEALTHCONNECTION (CONTINUED)

The three clinically recognized eating disorders are anorexia nervosa, bulimia nervosa, and binge eating disorder. The diagnostic criteria for each are listed in Table 14.8.

Anorexia Nervosa Involves Severe Kilocalorie Restriction Anorexia nervosa is a serious, potentially life-threatening eating disorder that is characterized by self-starvation and exces- sive weight loss. People who suffer from anorexia nervosa have an intense fear of gaining weight or being “fat.” This fear causes them to control their food intake by restricting the amount of food they con- sume, resulting in significant weight loss.

Many people with anorexia nervosa have a fear of eating certain foods, such as those that contain fat and sugar. They believe that these foods will make them “fat,” regardless of how little of them they eat. A distorted

anorexia nervosa Eating disorder in which people intentionally starve themselves, causing extreme weight loss.

Eating Disorder Diagnostic Criteria

Anorexia nervosa • Restriction of energy intake relative to requirements leading to a significantly low body weight in the context of age, sex, developmental trajectory, and physical health

• Intense fear of gaining weight or becoming fat, even though underweight

• Disturbance in the way one’s body weight or shape is experienced, excessive influence of body weight or shape on self-esteem or denial of the seriousness of the current low body weight

Bulimia nervosa • Recurrent episodes of binge eating. An episode of binge eating is characterized by both of the following: • Eating in a discrete amount of time (within a 2-hour

period) large amounts of food • Sense of lack of control over eating during an episode

• Recurrent inappropriate compensatory behavior in order to prevent weight gain (purging)

• The binge eating and compensatory behaviors both occur, on average, at least twice a week for 3 months

• Self-evaluation is unduly influenced by body shape and weight

• The disturbance does not occur exclusively during episodes of anorexia nervosa

Binge eating disorder (BED) • Recurrent and persistent episodes of binge eating. An episode of binge eating is characterized by both of the following: • Eating, in a discrete period of time, an amount of food

that is definitely larger than most people would eat in a similar period of time under similar circumstances

• A sense of lack of control over eating during the epi- sode (for example, a feeling that one cannot stop eat- ing or control what or how much one is eating)

• Binge eating episodes are associated with three (or more) of the following: • Eating much more rapidly than normal • Eating until feeling uncomfortably full • Eating large amounts of food when not feeling physi-

cally hungry • Eating alone because of being embarrassed by how

much one is eating • Feeling disgusted with oneself, depressed, or very

guilty after overeating • Marked distress regarding binge eating is present • The binge eating occurs, on average, at least once a

week for three months • The binge eating is not associated with the recurrent

use of inappropriate compensatory behavior (for exam- ple, purging) and does not occur exclusively during the course of anorexia nervosa, bulimia nervosa, or avoid- ant/restrictive food intake disorder

Other specified feeding or eating disorder (OSFED)

• A pattern of disordered eating that does not meet the criteria for anorexia nervosa, bulimia nervosa, or binge eating disorder; includes orthorexia and night eating syndrome

Source: American Psychiatric Association, Diagnostic and Statistical Manual of Mental Disorders (DSM-5®), 5th ed. (Arlington, VA: American Psychiatric Association, 2013).

TABLE 14.8 Diagnostic Criteria for Eating Disorders

Although the highest rates of disordered eating patterns occur among females, males are not immune. Adolescents in particular can feel pressure to achieve a certain body image.

HEALTHCONNECTION (CONTINUED)

What Is Disordered Eating? 529

body image How you perceive your physical appearance.

body image is also present. Typically, suf- ferers see themselves as fat even though they are underweight. They therefore continue to restrict their food intake in order to lose more weight. For instance, someone with anorexia nervosa might eat only a piece of fruit and a small container of yogurt during an entire day. Some may also exercise exces- sively as a means of controlling their weight.

Numerous health consequences can occur with anorexia nervosa and some can be fatal. One of the most serious is an electrolyte imbalance, specifically low blood potassium, which can lead to an irregular heart rhythm and cardiac arrest. Additionally, because of their extreme lack of body fat, their internal body temperature drops and they feel cold even when it is hot outside. In an effort to regulate body temperature, their body may begin to grow lanugo (downy hair), particularly on the face and arms. Loss of body fat also disrupts levels of reproduc- tive hormones, resulting in amenorrhea (ces- sation of menstruation) in women.

Because the body of a person with anorexia nervosa is not getting enough nutrients, nonessential body functions begin to slow or shut down in an effort to conserve energy for the most vital func- tions. The person may begin to experience a decrease in heart rate and blood pressure, overall weakness and fatigue, hair loss, and a slowing of digestive process, which often results in constipation, bloating, and delayed gastric emptying. Dehydration, iron deficiency, and osteoporosis can also result from inadequate nutrient intake.

Bulimia Nervosa Involves Cycles of Binge Eating and Purging Bulimia nervosa is another clinical eating disorder that can be life-threatening. Dur- ing times of binge eating, the person lacks control over eating and consumes larger than normal amounts of food in a short period of time. Following the binge, the person counters the excess food consump- tion with some type of purging. Many

lanugo Very fine, soft hair typically found on a newborn or a person who is malnourished.

bulimia nervosa Eating disorder character- ized by binging (consuming large quantities of food in a short period of time) and then purging through vomiting or other means.

people assume that bulimics always purge by vomiting, but purging can be described as any behavior that assists in “getting rid” of food to prevent weight gain or to pro- mote weight loss. This can include vigor- ous exercise, abuse of diet pills, laxatives, or diuretics, and strict dieting or fasting.

As with anorexia nervosa, people with bulimia nervosa often suffer from depres- sion and have low self-esteem. They may feel shame and guilt about their eating behaviors and may try to hide their eating problems from others. Those who have bulimia nervosa are overly concerned with body shape and weight, but usually do not have the same distorted body image as someone with anorexia nervosa.

People with bulimia nervosa often eat in secret.

Most of the health consequences that occur with bulimia nervosa are associated with self-induced vomiting, such as tearing of the esophagus, swollen parotid glands (the salivary glands located on each side of the face in front of the ears), tooth decay and gum disease (due to stomach acid), and broken blood vessels in the eyes (due to pressure from vomiting). One sign of bulimia nervosa is often scar tissue on the knuckles of a person’s fingers, which forms from their being frequently used to induce

vomiting. Electrolyte imbalance can occur with bulimia nervosa and can be fatal. Peo- ple with bulimia nervosa may experience dehydration and constipation due to fre- quent episodes of binge eating and purging.

Laxative abuse can cause serious medical complications. The repeated use of laxa- tives can cause constipation, dehydration due to fluid loss in the intestines, electrolyte imbalances, fluid retention, bloody stools, and impaired bowel function.

Binge Eating Disorder Involves Compulsive Overeating Binge eating disorder is characterized by recurrent episodes of binge eating without purging. People who have binge eating disorder eat without regard to physiological cues. They may eat for emo- tional reasons, which results in an out-of- control feeling while eating and physical and psychological discomfort after eating. Many people who struggle with this type of eating disorder will eat in secret and feel ashamed about their behaviors.

Because people who struggle with binge eating disorder do not typically purge, they are typically overweight or obese. Health effects therefore may include hypertension, high cholesterol levels, heart disease, type 2 diabetes, and gallbladder disease.

Other Disordered Eating Behaviors Can Be Harmful In addition to anorexia nervosa, bulimia nervosa, and binge eating disorder, there are other abnormal eating behaviors that

binge eating disorder Eating disorder char- acterized by recurrent episodes of binge eating without purging.

530 Chapter 14 | Energy Balance and Body Composition

HEALTHCONNECTION (CONTINUED)

can be harmful and require treatment. These include orthorexia, night eating syndrome, and pica.

Orthorexia is defined as an obsession with “healthy or righteous eating” and often begins with someone’s simple desire to live a healthy lifestyle. Someone with orthorexia fixates on defining the “right” foods, and will spend just as much time and energy thinking about food as someone with anorexia nervosa or bulimia nervosa. While this person may not obsess about calories, they think about the overall health benefits and how the food was processed, prepared, etc. Various factors can contribute to this obsession for healthy foods, including hear- ing something negative about a food or food group, which then leads to completely elimi- nating the food or foods from their diet. The restrictive nature of orthorexia has the potential to develop into anorexia nervosa.

Night eating syndrome is a unique combina- tion of disordered eating, a sleep disorder, and a mood disorder.19 Someone with this syndrome consumes the majority of daily kilocalories after the evening meal, as well as wakes up during the night, possibly even several times, to eat. In addition, the person typically does not have an appetite during the morning hours and consumes very little throughout the day. One study found that people with night eating syndrome con- sume 56 percent of their 24-hour kilocalo- rie intake between the hours of 8:00 p.m. and 6:00 a.m. This study also found that people with night eating syndrome gener- ally do not binge eat with each awakening; rather, they eat smaller portions of food on several occasions throughout the night.20

Pica refers to a strong, persistent desire to eat, lick, or chew non-nutritive sub- stances, such as clay, dirt, or chalk. Consum- ing nonfood substances can cause serious medical complications such as intestinal obstruction, intestinal perforation, infec- tions, or lead poisoning.

Because orthorexia and night eating syn- drome do not meet the diagnostic criteria for anorexia nervosa, bulimia nervosa, or binge eating disorder, but still require treat- ment, they fall into the diagnostic category of “other specified feeding and eating

disorders” (OSFED).21 Other behaviors in this category include purging without bing- ing, restrictive eating by people who are in a normal weight range despite having signifi- cant weight loss, binging and purging but not frequently enough to meet criteria for

bulimia, and chewing and spitting out food instead of swallowing it.

Different Eating Disorders Share Some Common Traits A common trait of people with eating dis- orders is obsession with food and eating.22 Unrealistic standards can produce a sense of self-loathing, guilt, and low self-esteem. Many people who struggle with eating disorders are trying to gain some control in their lives. When external factors feel out of control, they get a sense of security from being able to control food consumption and body weight. They may withdraw from social interactions where food is present and where they might have to eat around others. Also, depression is more common among people who have eating disorders as compared to the general population.23

You might know someone with an eat- ing disorder, but may not know how to help the person. First, learn the warning signs (Table 14.9). If you’re concerned about your own eating behaviors, take the

People with night eating syndrome may con- sume more than half their day’s kilocalories between 8:00 P.M. and 6:00 A.M.

Warning Sign Explanation/Example

Weight is below 85% of ideal body weight

Even if underweight, refusal to accept and maintain current body weight

Excessive exercise Often exercises daily for long periods of time to burn kilocalories and prevent weight gain. May skip work or class to exercise.

Preoccupation with food and weight

Constantly worries about amount and type of food eaten and potential weight gain. May check body weight daily or several times per day.

Refusal to eat appropri- ate variety and/or quan- tity of food

Will avoid food in order to lose weight or prevent weight gain. May avoid only certain foods, such as those with fat or sugar.

Avoidance of social eating

Wants to eat alone. Makes excuses to avoid eating with others.

Diet pill use or laxative use

Evidence of pill bottles, boxes, or packaging

Distorted body image Does not see himself/herself as he or she truly is. May comment on being fat even if underweight.

Changes in mood May become more withdrawn, depressed, or anxious, especially around food

Loss of menstrual period Periods become irregular or completely absent

Hair loss Hair becomes thinner and falls out in large quantities

TABLE 14.9 Warning Signs for Eating Disorders

HEALTHCONNECTION (CONTINUED)

What Is Disordered Eating? 531

Self-Assessment “Are You at Risk for an Eating Disorder?” to find out.

If you are concerned about a friend’s eating behaviors, find a good time and place to gently express your concerns with- out criticism or judgment. Realize that you may be rejected or your friend may deny the problem. Be supportive and let the per- son know that you are available if they want to talk to you at another time. You should also realize that there are many things that you cannot do to help a loved one or friend get better. You cannot force an anorexic to eat, keep a bulimic from purging, or make a binge eater stop overeating. It is up to the

Self-Assessment

Are You at Risk for an Eating Disorder? Mark the following statements True or False to help you find out.

1. I constantly think about eating, weight, and body size.

True □ False □

2. I’m terrified about being overweight.

True □ False □

3. I binge eat and can’t stop until I feel sick.

True □ False □

4. I weigh myself several times each day.

True □ False □

5. I exercise too much or get very rigid about my exercise plan.

True □ False □

6. I have taken laxatives or forced myself to vomit after eating.

True □ False □

7. I believe food controls my life.

True □ False □

8. I feel extremely guilty after eating.

True □ False □

9. I eat when I am nervous, anxious, lonely, or depressed.

True □ False □

10. I believe my weight controls what I do.

True □ False □

Analysis These statements are designed to help you identify potentially problematic eating behav- ior. These statements do not tell you if you have an eating disorder. Look carefully at any statement you marked as true and decide if this behavior prevents you from enjoying life or makes you unhealthy. Changing these behaviors should be done gradually, making small changes one at a time. Contact your student health services center or your health care provider if you suspect you need help. Adapted from National Eating Disorders Association. 2016. Available at https://www.nationaleatingdisorders .org/learn/help/educators/school-setting. Accessed April 2017.

individual to decide when he or she is ready to deal with the issues in life that led to the eating disorder.

Eating Disorders Can Be Treated The most effective treatment for eat- ing disorders is a multidisciplinary team approach including psychological, medi- cal, and nutrition professionals. All mem- bers of the team should be knowledgeable and experienced with eating disorders treatment. A physician or other medical professional should closely monitor the

person. In severe cases, a physician may require the patient to be hospitalized as part of the treatment. A psychologist can help the person deal with emotional and other psychological issues that may be contributing to the eating disorder.

A registered dietitian nutritionist can help someone with an eating disorder establish normal eating behaviors. Some nutritional approaches to eating disorders include identifying binge triggers, safe and unsafe foods, and hunger and fullness cues. Food journals are often helpful to identify eating patterns, food choices, moods, disor- dered eating triggers, eating cues, and timing of meals and snacks. Meal plans are also used in some instances to ensure adequate kilocalorie and nutrient intake among those with anorexia nervosa and to help avoid overeating among those with bulimia ner- vosa or binge eating disorder.

Most people recover from eating dis- orders. When treatment is sought in the early stages, there is a better chance that the person will recover fully and have a shorter recovery process than someone who begins treatment after many years. In some people, the recovery process takes years. Some con- tinue throughout life to have the desire to engage in disordered eating behaviors; how- ever, they are able to refrain from actually engaging in these behaviors. Unfortunately, some individuals never fully recover.

LO 14.6: THE TAKE-HOME MESSAGE Disordered eating is characterized by an abnormal eating pattern. Eating disorders are psychiatric disorders diagnosed in people who meet specific diagnostic criteria. The three clinical eating disorders are anorexia nervosa, bulimia ner- vosa, and binge eating disorder. Eating disorders are most effec- tively treated with a multidisciplinary approach including psychological, medical, and nutrition profession- als. A full recovery takes time but is possible, especially if the disorder is treated in the early stages.

532 Chapter 14 | Energy Balance and Body Composition

Visual Chapter Summary

LO 14.1 Energy Balance Is Achieved When Energy In Equals Energy Out Energy balance is the relationship between energy con- sumed and energy expended. Body weight remains con- stant when energy intake equals energy expenditure. When more energy is consumed than expended, the body is in positive energy balance and weight gain occurs. When the intake of kilocalories falls short of energy needs or you expend more energy than you consume, the body is in negative energy balance and weight loss occurs.

ENERGY INTAKE = ENERGY EXPENDITURE

WEIGHT MAINTENANCE

BMR 50–70%

TEF 10%

TEE (includes adaptive thermogenesis and

NEAT) ~20–35%

Total Daily Energy Expenditure (TDEE)

LO 14.2 Three Factors Contribute to TDEE Total daily energy expen- diture (TDEE) is the sum of energy expended on basal metabolism, the thermic effect of food (TEF), and the thermic effect of exercise (TEE). An individual’s basal metabolic rate (BMR) is influenced mainly by lean body mass. The ther- mic effect of food is the energy used to process recently eaten foods. The thermic effect of exercise (TEE) includes the energy required to exercise, maintain posture while standing and sitting, and engage in nonexercise activity thermogenesis, or NEAT, which is all activity that is not structured exercise, including unconscious muscle activity.

LO 14.3 Energy Expenditure Can Be Measured Directly or Indirectly Energy expenditure can be measured directly with a metabolic chamber or indirectly based on oxygen consumed and carbon dioxide produced during activity. The estimated energy require- ment (EER) can be calculated using an individu- al’s age, weight, height, and physical activity level.

LO 14.4 Body Composition Is a Ratio of Fat to Lean Body Mass Body composition refers to the ratio of fat to lean body mass and is mea- sured as a percent body fat. Total body fat comprises essential fat, found in bone marrow, organs, muscles, and the central nervous system, and storage fat, found in adipose tissue. Stored fat can be visceral, located around the organs, or subcutaneous, located just beneath the skin. White adipose tissue is primarily a storage tissue; brown adipose tissue contains more mitochon- dria, is rich in blood, and generates heat.

The placement of body fat also affects overall health. Storing excess fat around the waist has been shown to increase the risk of heart disease, diabetes, and hypertension. The more visceral fat stored near the liver, the greater the risk of insulin resistance, hyperlipidemia, and low levels of HDL cholesterol, all of which increase the risk of heart disease and diabetes.

The most accurate instrument to measure body composition is dual-energy X-ray absorptiometry (DEXA). Body composition is also estimated from body volume using hydrostatic weighing and air displace- ment plethysmography. Bioelectrical impedance analysis measures resis- tance by body fat; skinfold calipers estimate subcutaneous fat; and waist circumference measures android obesity.

Visual Chapter Summary 533

LO 14.5 BMI Is Used to Determine Body Weight and Health Risks Reference standards have been devel- oped as indirect measurements of a healthy body weight. Body mass index (BMI) is a calculation of body weight related to height and is correlated with health risks. A BMI of 18.5924.9 kg/m2 is considered healthy. A BMI from 25 to 29.9 kg/m2 is considered overweight and a BMI of 30 kg/m2 or greater is considered obese. A BMI lower than 18.5 kg/m2 is considered underweight.

A healthy body weight doesn’t increase the risk of any weight-related health problems. Overweight and obesity increase the individual’s risk of chronic disease and premature death. Under- weight is also associated with a variety of health risks, including an increased risk of premature death.

LO 14.6 Eating Disorders Are Psychiatric Disorders Disordered eating describes a variety of abnormal eating patterns, such as restric- tive eating, binge eating, vomiting after eating, and abusing laxatives or diet pills. Eating disorders are psychiatric disorders diagnosed according to specific criteria that include disordered eating behaviors and other factors.

Anorexia nervosa is characterized by self-starvation and excessive weight loss. Bulimia nervosa involves repeated cycles of binge eating and purging. Binge eat- ing disorders are characterized by binge eating without purging. Night eating syndrome is described as excessive kilo- calorie intake in the evening and waking up during the night to eat.

The most effective treatment for eat- ing disorders involves a multidisciplinary team approach including psychological, nutrition, and medical professionals.

Extremely High Risk BMI 40+ and high waist circumference

Very High Risk BMI 30–39.9 and high waist circumference

High Risk BMI 25–29.9 and high waist circumference or BMI 30–34.9 and low waist circumference

Increased Risk BMI 25–29.9 and low waist circumference

Low Risk BMI under 25

Terms to Know ■ energy balance ■ positive energy balance ■ negative energy balance ■ bomb calorimeter ■ physiological fuel values ■ total daily energy expenditure (TDEE) ■ basal metabolism ■ basal metabolic rate (BMR) ■ lean body mass (LBM) ■ resting metabolic rate (RMR) ■ thermic effect of food (TEF) ■ thermogenesis ■ thermic effect of exercise (TEE) ■ nonexercise activity thermogenesis

(NEAT) ■ direct calorimetry ■ indirect calorimetry ■ estimated energy requirement (EER) ■ body composition ■ essential fat ■ subcutaneous fat ■ visceral fat

■ brown adipose tissue (BAT) ■ central (android) obesity ■ gynoid obesity ■ hydrostatic weighing ■ air-displacement plethysmography ■ dual-energy X-ray absorptiometry

(DEXA) ■ bioelectrical impedance analysis (BIA) ■ skinfold caliper ■ waist circumference ■ body mass index (BMI) ■ healthy weight ■ underweight ■ overweight ■ obese ■ severe obesity ■ disordered eating ■ eating disorders ■ anorexia nervosa ■ body image ■ lanugo ■ bulimia nervosa ■ binge eating disorder

534 Chapter 14 | Energy Balance and Body Composition

Mastering Nutrition Visit the Study Area in Mastering Nutrition to hear an MP3 chapter summary.

Check Your Understanding LO 14.1 1. An individual who is regu-

larly in negative energy balance will most likely a. lose weight. b. gain weight. c. maintain current body

weight. d. burn more muscle weight

than fat weight. LO 14.1 2. A negative energy balance

means that you a. eat more than you burn off

in total kilocalories. b. eat less than you burn off in

total kilocalories. c. are gaining weight. d. are maintaining weight.

LO 14.2 3. The basal metabolic rate (BMR) is a measure of a. the amount of energy

expended during physical activity.

b. the amount of energy expended during digestion.

c. the amount of energy con- sumed daily.

d. the amount of energy expended to meet basic physiological needs.

LO 14.2 4. Will’s breakfast contains 525 kilocalories. How many kilo- calories will he expend (TEF) to process this meal? a. 5–10 kilocalories b. 50–100 kilocalories c. 125–140 kilocalories d. 150–175 kilocalories

LO 14.3 5. An individual’s estimated energy requirement is based on all of the following except: a. body posture. b. age. c. activity level. d. gender.

LO 14.4 6. The method that uses the fact that lean tissue is denser than water to measure body composition is called a. air-displacement

plethysmography. b. bioelectrical impedance

analysis. c. dual-energy X-ray

absorptiometry. d. hydrostatic weighing.

LO 14.4 7. Approximately what per- centage of the body is made up of essential fat? a. 9 percent for women, 5 per-

cent for men b. 15 percent for women, 18

percent for men c. 12 percent for women, 3

percent for men d. 18 percent for women, 20

percent for men LO 14.5 8. Being underweight increases

the risk of which of the following? a. Premature death b. Cancer c. Heart disease d. Diabetes

LO 14.6 9. Which of the following is a clinical eating disorder? a. Orthorexia b. Night eating syndrome c. Pica d. Binge eating disorder

LO 14.6 10. What causes those who suffer from anorexia nervosa to control their food intake? a. Intense distaste for healthy

foods b. Loss of appetite c. Busy lifestyle d. Intense fear of becoming

overweight

Answers 1. (a) Negative energy balance means

the amount of energy intake is less than the energy output. If main- tained over time, negative energy bal- ance most likely results in weight loss.

2. (b) If you are in negative energy bal- ance, you are consuming fewer kilo- calories than you expend. You are in energy balance when your weight

is stable—you are consuming and expending the same number of kilo- calories. You are in positive energy balance when you are consuming more energy than you expend.

3. (d) BMR is a measure of the amount of energy needed to meet basic physiological needs; for example, to maintain cellular functions and keep blood circulating and lungs breath- ing. The amount of energy expended during physical activity is not fac- tored into the BMR. The energy cost of digesting, absorbing, and processing food is called the thermic effect of food (TEF) and is also not part of BMR. The amount of energy consumed doesn’t factor into the BMR.

4. (b) The thermic effect of food costs approximately 10 percent of the total kilocalories to process a normal mixed meal. Ten percent of 525 kilo- calories equals 52 kilocalories.

5. (a) Estimated energy requirement is based on gender, age, and activity level. Body posture is not a factor.

6. (d) Hydrostatic weighing is the method used to measure body composition based on the fact that lean tissue is denser than water. Air- displacement plethysmography is based on the amount of air the body displaces. Bioelectrical impedance measures the resistance of a current by body fat, and dual-energy X-ray absorptiometry measures body fat by passing X-rays through fat-free mass and fat mass.

7. (c) Essential body fat makes up approximately 12 percent of total body fat for women and 3 percent for men.

8. (a) Being underweight increases the risk of premature death. Being over- weight increases the risk of develop- ing diabetes, cancer, or heart disease.

9. (d) Binge eating disorder is a clini- cal eating disorder. Night eating syndrome, orthorexia, and pica are patterns of behavior involving disor- dered eating but are not classified as psychiatric disorders.

10. (d) An intense fear of becoming overweight generally causes those who suffer from anorexia nervosa to control their food intake.

References 535

Answers to True or False? 1. True. Technically, exercise isn’t

necessary to produce a negative energy balance. People who are ill, for example, commonly lose weight, as do breastfeeding mothers. Exercise is, however, an important component of healthy weight loss programs, because in addition to burning kilocalories directly, it speeds up your metabolism and has multiple health benefits.

2. False. Being underweight increases the risk of serious health conse- quences, including anemia, heart irregularities, osteoporosis, amenor- rhea, depression, and anxiety. It can therefore be more harmful to health than moderate overweight.

3. True. Males have a higher basal metabolic rate than females mostly because they have more muscle mass and lower levels of body fat. This means that men, on average, burn more kilocalories than women.

4. True. The Dietary Guidelines for Ameri- cans recommend using weight for height or body mass index calcula- tions to estimate whether you are at a healthy weight.

5. False. Android obesity, or storing excess fat around the abdomen, puts an individual at higher risk for car- diovascular disease and diabetes than does gynoid obesity, which is the storage of excess fat around the hips.

6. False. Body weight is a sum of an individual’s body fat plus lean body mass, whereas body composition indicates the ratios of body fat to total body weight and lean body mass to total body weight.

7. False. If you eat an extra 100 kilocal- ories per day for a week, that is equal to 700 additional kilocalories, not the 3,500 kilocalories needed to gain a pound.

8. True. Skinfold calipers are an inexpen- sive and practical method for measur- ing body composition in a gym or recreation center. Fitness labs use more expensive and more precise tools.

9. False. Disordered eating describes a variety of eating patterns considered abnormal and potentially harmful. Eating disorders are diagnosed by

clinicians according to specific cri- teria that include disordered eating behaviors as well as other factors. It is possible for someone to engage in disordered eating without having an actual eating disorder.

10. True. The long-term starvation of anorexia nervosa and consistent purg- ing of bulimia nervosa (which can lead to electrolyte imbalance) can be fatal.

Web Resources ■ For more on overweight and obesity,

visit the Centers for Disease Control and Prevention at www.cdc.gov

■ For more information on assessing body composition and health risks, visit the National Heart, Lung, and Blood Institute at www.nhlbi.nih.gov

■ Additional information on eating disorders and their prevention and treatment can be found at the National Eating Disorders Association at www.nationaleatingdisorders.org

References 1. Merrill, A. L., and B. K. Watt. 1973. Energy

Values of Foods: Basis and Derivation. Agricultural Handbook no. 74. Washington, DC: USDA.

2. Apolzan, J. W., H. J. Leidy, R. D. Mattes, and W. W. Campbell. 2011. Effects of Food Form on Food Intake and Postprandial Appetite Sensations, Glucose and Endocrine Responses, and Energy Expenditure in Resis- tance Trained v. Sedentary Older Adults. Brit- ish Journal of Nutrition 106(7):1107–1116.

3. Petzke, K. J., A. Freudenberg, and S. Klaus. 2014. Beyond the Role of Dietary Protein and Amino Acids in the Prevention of Diet- Induced Obesity. International Journal of Molec- ular Sciences 15(1):1374–1391. doi: 10.3390/ ijms15011374.

4. Wu, C. S., O. Y. N. Bongmba, J. Yue, J. H. Lee, L. Lin, K. Saito, et al. 2017. Suppression of GHS-R in AgRP Neurons Mitigates Diet- Induced Obesity by Activating Thermogen- esis. International Journal of Molecular Science 18:832.

5. Ibid. 6. Pedersen, S. J., P. D. Cooley, and C. Mains-

bridge. 2013. An E-Health Intervention Designed to Increase Workday Energy Expenditure by Reducing Prolonged Occu- pational Sitting Habits. Work. doi: 10.3233/ WOR-131644.

7. Food and Nutrition Board. 2005. Dietary Reference Intakes for Energy, Carbohydrate, Fiber, Fat, Fatty Acids, Cholesterol, Protein, and Amino Acids (Macronutrients). Washington, DC: National Academies Press.

8. Ibid.

9. Orava, J., L. Nummenmaa, T. Noponen, T. Viljanen, R. Parkkola, P. Nuutila, and K. A. Virtanen. 2014. Brown Adipose Tissue Function Is Accompanied by Cerebral Acti- vation in Lean But Not in Obese Humans. Journal of Cerebral Blood Flow and Metabolism. doi: 10.1038/jcbfm.2014.50.

10. National Institutes of Health. 2000. Clinical Guidelines on the Identification, Evaluation, and Treatment of Overweight and Obesity in Adults. Available at www.nhlbi.nih.gov. Accessed April 2017.

11. Tanisawa, K., H. Taniguchi, X. Sun, T. Ito, R. Kawakami, S. Sakamoto, and M. Higuchi. 2017. Visceral Fat Area is a Strong Predictor of Leukocyte Cell-Derived Chemotaxin 2, a Potential Biomarker of Dyslipidemia. PLoS ONE 12(3):e0173310. doi: 10.1371/journal. pone.0173310.

12. Centers for Disease Control and Prevention. 2013. Body Mass Index: Considerations for Prac- tioners. Available at www.cdc.gov. Accessed April 2017.

13. National Institutes of Health. 2000. Clinical Guidelines on the Identification, Evaluation, and Treatment of Overweight and Obesity in Adults.

14. Diemer, E. W., J. D. Grant, M. A. Munn- Chernoff, D. Patterson, and A. E. Duncan. (2015). Gender Identity, Sexual Orientation, and Eating-Related Pathology in a National Sample of College Students. Journal of Adolescent Health 57(2):144–149.

15. Schoenefeld, S. J., and J. B. Webb. 2013. Self-Compassion and Intuitive Eating in College Women: Examining the Contribu- tions of Distress Tolerance and Body Image Acceptance and Action. Eating Behaviors 14(4):493–496.

16. Räisänen, U., and K. Hunt. 2014. The Role of Gendered Constructions of Eating Dis- orders in Delayed Help-Seeking in Men: A Qualitative Interview Study. British Medical Journal Open 4(4):e004342.

17. Chao, A. M., C. M. Grilo, and R. Sinha. 2016. Food Cravings, Binge Eating, and Eating Disorder Psychopathology: Exploring the Moderating Roles of Gender and Race. Eating Behaviors 21:41–47. doi: 10.1016/j. eatbeh.2015.12.007.

18. Ibid. 19. Kucukgoncu, S., M. Midura, and C. Tek.

2015. Optimal Management of Night Eating Syndrome: Challenges and Solutions. Neu- ropsychiatric Disease and Treatment 11:751–760. doi: 10.2147/NDT.S70312.

20. Ibid. 21. Diagnostic and Statistical Manual of Mental

Disorders (DSM-5®), Fifth Edition. 2015. Washington, DC: American Psychiatric Association.

22. National Eating Disorders Collaboration. 2016. What Is an Eating Disorder? Available at http://nedc.com.au/eating-disorders- explained. Accessed April 2017.

23. Eating Disorders: A Professional Resource for General Practitioners. 2014. Available at http://www.nedc.com.au/files/Resources// GPs%20Resource.pdf. Accessed April 2017.