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Questions and Answers A Guide to Fitness and Wellness 4th Edition

Gary Liguori │ Sandra Carroll-Cobb

©McGraw-Hill Education. All rights reserved. Authorized only for instructor use in the classroom. No reproduction or further distribution permitted without the prior written consent of McGraw-Hill Education.

CHAPTER 7

Body Composition Basics

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COMING UP IN THIS CHAPTER

Understand the basic composition of your body

Identify factors that influence your body composition

Examine the relationship between body composition and health

Assess your body composition

Identify strategies for making changes in your body composition

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Basics of Body Composition, 1

Question: What is body composition?

Body composition: the makeup of the body

The relative proportions of different types of body tissues

Muscle

Bone

Fat

Other vital tissues

Percent body fat is the measure most often used to define and evaluate body composition

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Basics of Body Composition, 2

Question: Is there such a thing as good body fat?

The body needs fat in order to function

Essential fat

Found in bone marrow, muscles, and various organs

Surrounds nerve fibers in the brain, allowing for the transmission of messages

A key component of cell membranes

Important in healthy hormone production

8–12% in females and 3–5% in males

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Basics of Body Composition, 3

Storage fat (adipose tissue)

Site for storage of energy

Also releases molecules and hormones that affect appetite, blood pressure, immune system function, and insulin and glucose levels

Too much has negative health effects

Visceral fat

Found deep within the abdominal cavity

Surrounds internal organs

Subcutaneous fat

Found just beneath the skin

Insulates the body and regulates temperature

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Basics of Body Composition, 4

Question: My friends and I look about the same, but most of them weigh around 15 pounds less than I do. How is that possible?

Differences in tissue density

Differences between muscle and fat

Differences in body composition

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FIGURE 7-1 BODY COMPOSITION OF YOUNG ADULTS (AGES 20–24)

Left photo: ©shipfactory/Shutterstock.com RF; Right photo: ©Vladyslav Starozhylov/Shutterstock.com RF

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FIGURE 7-2 VISCERAL AND SUBCUTANEOUS FAT IN THE ABDOMEN

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Basics of Body Composition, 5

Question: What is metabolism?

Metabolism: all the processes that require energy (calories from foods) and maintain body functioning

Energy balance: the connection between metabolism and body composition

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Basics of Body Composition, 6

The amount of energy your body requires depends on three criteria:

Resting metabolic rate (RMR)

Energy required to maintain essential processes at rest

Depends on genetics, body size, and body composition

Muscle is more metabolically active than fat

Resistance training increases RMR

Dietary thermogenesis

The energy required to digest and process food

Physical activity

Energy expended in daily living as well as formal exercise

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Basics of Body Composition, 7

Question: How do we get fat, literally? What causes the body to retain fat, and where does it go?

The body produces and stores fat when more energy is consumed than is used to maintain body functions and fuel activities

Protects from starvation

3,500 calories is the equivalent of a pound of body weight

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Basics of Body Composition, 8

Most fat is stored in fat deposits, which are about 80% fat and 20% support cells, immune cells, and blood vessels

If you gain weight as fat, these fat cells enlarge, storing more fat

If you lose body fat, your fat cells shrink

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Basics of Body Composition, 9

Question: Do overweight and obese mean the same thing?

Obesity is considered more extreme and serious

Overweight: weight above a recommended range, based on large-scale population surveys or studies

Obesity: higher degree of overweight, characterized by excessive body fat

Height and waist circumference are also considered in evaluating health risks

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Basics of Body Composition, 10

Question: Have Americans gotten fatter?

On average, the American population has become heavier

The average weight for adults in their twenties is 15 pounds heavier today than 20 years ago

The prevalence of obesity has increased significantly

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FIGURE 7-3 TRENDS IN OVERWEIGHT AND OBESITY AMONG U.S. ADULTS, 1962–2014

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Factors Affecting Body Composition

Question: Do shorter people have a higher body-fat percentage?

Body composition is based on a combination of factors

Height is related, but it doesn’t predict the amount of body fat within your body

Height is a body composition factor not in your control

Some of the other factors, you can control

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Genetics, 1

Question: Is my body composition going to be similar to that of my parents? Is body composition based at all on genetics?

The contribution of heredity will be between 25% and 75%

Hundreds of genes affect body fat

INSIG2 and FTO genes

Influence body size; amount and distribution of body fat; and response to exercise

Body composition is also influenced by numerous environmental factors

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Genetics, 2

Question: Why is it so hard for skinny guys to gain muscle mass?

High resting metabolic rate

Bodies that aren’t designed for muscle gain

Can build muscle, but won’t be able to radically change body type

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Biological Sex, 1

Question: I know men’s and women’s bodies are different, but when my boyfriend and I eat together, it seems as if I am more susceptible to weight gain than he is. Why?

Body composition differs between the sexes and varies with age

Birth weights

Young years

Adolescence and puberty

Midlife

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FIGURE 7-4 AVERAGE PERCENT OF BODY FAT BY AGE AND SEX

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Biological Sex, 2

Question: Why do men gain fat in their belly, and women in their hips?

Men are more likely to store excess fat in the abdomen; women, in hips and thighs

Android: apple-shaped; more common in men and postmenopausal women

Gynoid: pear-shaped; more common in premenopausal women

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FIGURE 7-5 BODY-FAT DISTRIBUTION

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Age

Question: Does body composition always get worse as we get older?

It is hard to separate the effects of age from use

Less physical activity and exercise:

With each decade they don’t strength train, adults lose about 4–6 pounds of muscle mass, and their resting metabolic rate also declines

Physical activity and exercise, especially resistance training, can maintain muscle mass through the aging process

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Ethnicity

Question: Do different ethnic groups have different body compositions?

Body composition patterns related to sex and age are consistent across all ethnic groups

However, ethnic differences have been found in average height, weight, and body composition

Differences related to culture and ethnicity

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TABLE 7-1 COMPARISON OF AVERAGE HEIGHT, WEIGHT, BODY MASS INDEX, AND TOTAL ABDOMINAL FAT AMONG ADULTS FROM FOUR ETHNIC GROUPS

	WHITE	AFRICAN AMERICAN	LATINO	ASIAN AMERICAN
MEN
HEIGHT	69 inches	69 inches	67 inches	67 inches
WEIGHT	176 pounds	177 pounds	173 pounds	152 pounds
BODY MASS INDEX**	25.7	26.0	27.1	23.6
ABDOMINAL FAT	9.3 pounds	7.9 pounds	9.1 pounds	9.9 pounds
PERCENT BODY FAT	20.4%	18.6%	20.9%	22.5%
WOMEN
HEIGHT	64 inches	64 inches	61 inches	62 inches
WEIGHT	156 pounds	174 pounds	150 pounds	120 pounds
BODY MASS INDEX**	27.0	29.2	28.4	22.2
ABDOMINAL FAT	12.7 pounds	12.2 pounds	12.7 pounds	13.3 pounds
PERCENT BODY FAT	35.6%	35.3%	37.4%	36.8%

*Based on measurement and dual-energy X-ray absorptiometry of 604 men and 1,192 women ages 18–96 years.

**Body mass index, a measure of relative body weight, is covered later in this chapter.

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Lifestyle and Environment, 1

Question: Some of my cousins are really fat, but my brothers and I are skinny. Why aren’t we more alike since we have many of the same genes?

Genetics, age, and sex are factors in body composition, but different lifestyles and environments also play a role

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Lifestyle and Environment, 2

Energy intake: if you consume more calories than you burn, you will gain weight

Physical activity: daily activity and exercise affect energy balance and body composition

Sleep: insufficient sleep is associated with increased body fat; may interfere with the ability to regulate appetite; and increases the risk of diabetes

Stress: psychological stress linked to increased energy intake, weight gain, and excess abdominal fat, along with insulin resistance

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Body Composition and Wellness

Question: Why is it important to know how much fat is in your body? What can one statistic like percent body fat tell you about health?

Body composition is one component of health-related fitness

Maintaining an appropriate level of body fat is vital to a healthy, longer life

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Problems Associated with Excess Body Fat, 1

Question: My dad is really big (I don’t like to say “fat”) and I worry about him. What are his greatest health risks?

Cardiovascular disease

High blood pressure and unhealthy blood fat levels

Type 2 diabetes

There is a direct relationship between excess body fat and type 2 diabetes

Cancer

Increased cancer risk of the breast, prostate, colon, pancreas, esophagus, endometrium, and kidney

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Problems Associated with Excess Body Fat, 2

Other problems associated with excess body fat:

Joint problems

Osteoarthritis

Sleep apnea

Asthma

Gallbladder and liver diseases

Reproductive problems

Shortened life expectancy

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Problems Associated with Excess Body Fat, 3

Question: Can you be sort of overweight or overfat and healthy at the same time?

The consequences of excess body fat and weight are controversial and the subject of ongoing research

Certain factors can make a difference

Age and weight history

An overweight youngster will be exposed to the effects of overweight for a longer period

We usually gain fat and weight as we age

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Problems Associated with Excess Body Fat, 4

Body-fat distribution

There is greater risk if excess is stored in the abdomen rather than in the hips and thighs

Other health risk factors

Additional risk factors: high blood pressure, elevated glucose

Lifestyle

Regular exercise can improve body composition and reduce risks associated with being overweight

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Problems Associated with Excess Body Fat, 5

Question: What is the lowest body-fat percentage you can have and still maintain a healthy lifestyle? Is it even possible for a woman to have absolutely no body fat?

It is not possible for anyone to have zero body fat

A certain amount of body fat is essential for proper body function

Consequences of low body fat, being underweight:

Fluid imbalances, vitamin and mineral deficiencies, kidney problems

Loss of bone mass, osteoporosis

Reproductive disorders

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Problems Associated with Excess Body Fat, 6

Question: If I exercise a lot and my period stops, is that a good thing or a bad thing?

Female athlete triad

Energy availability

Low energy as a result of insufficient calorie intake or increased energy expenditure without increased calorie intake

Menstruation

Amenorrhea

Bone health

Reduced bone density

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FIGURE 7-6 THE FEMALE ATHLETE TRIAD

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Body Composition and Athletic Performance

Question: I’m a runner. Will decreasing my body fat help make me faster?

Many factors beyond body composition determine performance

All being equal, a decreased level of body fat (that is still in the healthy range) might improve your performance and reduce your susceptibility to performance-related injuries

Too little energy intake and body fat can harm both health and athletic performance

There is no ideal percent body fat for each sport

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Body Composition, Body Image, and Emotional Wellness, 1

Question: What exactly is body image?

Body image: a mental picture of your own body and how you feel about it

Body dysmorphic disorder (BDD)—preoccupation with an imagined defect in appearance

Those with BDD generally have low self-esteem and may engage in compulsive behaviors

More common in women

Muscle dysmorphia—obsessed with the idea that one’s muscularity isn’t enough

More common in men

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Body Composition, Body Image, and Emotional Wellness, 2

Question: Where does body image come from?

The two key sources of body image (and self-esteem) are family and the media

Family life

Parents criticize the look of their children

Friends and teachers also have an influence

Media

Fashion magazines

TV shows and TV commercials

Social networking

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FIGURE 7-7 AVERAGE YOUNG WOMEN VERSUS FASHION MODELS AND MISS AMERICA (1920S–2000S)

(left): Source: Library of Congress, Prints & Photographs Division [LC-USZ62-78689]; (right): ©McGraw-Hill Education/Lars A. Niki, photographer

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Body Composition, Body Image, and Emotional Wellness, 3

Question: So we’re supposed to worry about how we look for health reasons but not worry about how we look. How does that work?

What’s important is what’s healthy

Assess your body composition according to health criteria

Avoid comparing yourself to unachievable ideals

Instead, change the way you think about your body

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Body Composition, Body Image, and Emotional Wellness, 4

Accepting your body:

Focus on the positives

Focus on health and healthy habits

Realistically evaluate which aspects of your body you can change

Set goals that are small and attainable

Avoid negative self-talk about your body

Recognize advertisements from the fitness and beauty industries as what they are

Don’t judge the appearance of others

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Assessing Body Composition

Question: What’s my ideal weight?

It is hard to define an ideal weight

It depends on other health risk factors

Consider body composition

Percent fat is a better indicator of health status than scale weight

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Body Mass Index: An Indirect Measure, 1

Question: How do I determine my BMI?

Body mass index (BMI)

One of most common techniques for assessing body fat

Weight(kg) / Height2(m)

BMI does not take into account muscle mass

Waist circumference is used to classify health risks associated with different BMI values

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Body Mass Index: An Indirect Measure, 2

Question: Is BMI relevant and accurate for both athletes and people who are out of shape?

BMI is only an indirect measure of body composition

It is less accurate for athletes, those with above-average muscle mass, older adults, and certain ethnic groups

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FIGURE 7-8 BODY MASS INDEX

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TABLE 7-2 BODY MASS INDEX (BMI) CLASSIFICATION AND DISEASE RISK

DISEASE RISK RELATIVE TO NORMAL WEIGHT AND WAIST CIRCUMFERENCE*

	BMI (KILOGRAM/METER2)	MEN: WAIST 40 INCHES (102 CENTIMETERS) WOMEN: WAIST 35 INCHES (88 CENTIMETERS)	MEN: WAIST 40 INCHES (102 CENTIMETERS) WOMEN: WAIST35 INCHES (88 CENTIMETERS)
UNDERWEIGHT	18.5
NORMAL OR HEALTHY WEIGHT	18.5–24.9
OVERWEIGHT	25.0–29.9	Increased	High
OBESE	30.0–34.9 35.0–39.9 40.0	High Very high Extremely high	Very high Very high Extremely high

*Disease risk for type 2 diabetes, hypertension, and cardiovascular disease; increased waist circumference can be a marker for increased risk even in persons of normal weight.

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Methods for Estimating Percent Body Fat, 1

Question: How can you determine body-fat percentages?

Skinfold measurements

Underwater (hydrostatic) weighing

Bioelectrical impedance analysis (BIA)

Air displacement plethysmography

Dual X-ray absorptiometry (DXA)

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TABLE 7-3 PERCENT-BODY-FAT ASSESSMENT METHODS

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Methods for Estimating Percent Body Fat, 2

Question: What’s the right percent body fat for me?

This depends on your age, sex, current body composition, and health status

Goals are important too

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FIGURE 7-9 PERCENT-BODY-FAT STANDARDS FOR MEN AND WOMEN

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Methods for Assessing Body-Fat Distribution

Question: Does body shape make any difference when assessing weight and percent body fat?

Body shape makes a difference

Waist circumference

Waist-to-hip ratio

Waist-to-height ratio

These provide some estimate of the risks associated with abdominal fat

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Making Changes in Body Composition, 1

Question: What’s a good goal for body weight and body fat?

Set appropriate goals based on health assessments and health-risk factors

Apply SMART criteria

Seek medical advice if necessary

Track your progress toward goals

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Making Changes in Body Composition, 2

Question: What’s the best way to lose body fat?

Focus on energy balance

Look at both sides of the energy balance equation

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FIGURE 7-10 ENERGY BALANCE

(cookie): ©Brand X Pictures/PunchStock RF; (swiss cheese): ©Photodisc/PunchStock/Getty Images RF; (beer): ©Burke/Triolo Productions/Getty Images RF; (bok choy): ©Stockdisc/PunchStock/Getty images RF; (young man): ©Rubberball Productions/Getty Images RF

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Making Changes in Body Composition, 3

Question: Why do I lose weight but not body fat?

Weight loss does not automatically equal fat loss

Dieting alone is not the best way to decrease body fat and improve body composition

The best programs for fat loss include increased exercise and modest reductions in energy intake

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Making Changes in Body Composition, 4

Question: What’s the best kind of exercise to lose body fat?

On the “energy out” side of the scale, body composition is best improved by a combination of exercise activities

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Making Changes in Body Composition, 5

Question: How much exercise do I need to maintain my weight range over time?

To prevent weight gain:

A minimum of 150 minutes per week of moderate-intensity aerobic exercise, or 75 minutes of vigorous-intensity exercise

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Making Changes in Body Composition, 6

To lose a modest amount of weight or to maintain weight loss:

More is better: 50 minutes a day of moderate-intensity exercise or 25 minutes of high-intensity exercise

To lose significant amounts of weight:

300 minutes per week of moderate-intensity exercise or 150 minutes high-intensity exercise

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TABLE 7-4 APPROXIMATE CALORIE COSTS OF SELECTED PHYSICAL ACTIVITIES

ACTIVITY	CALORIES PER POUND PER MINUTE*
Sitting in class or at computer	0.014
Child care (dressing, bathing)	0.023
Vacuuming or heavy cleaning	0.026
Shoveling snow	0.045
Walking, brisk (3.5 miles per hour)	0.029
Walking, very brisk (4.5 miles per hour)	0.048
Jogging, moderate (5 miles per hour, 12 minutes per mile)	0.060
Jogging (7.5 miles per hour, 8 minutes per mile)	0.095
Cycling, light effort	0.045
Cycling, moderate	0.060
Cycling, vigorous	0.076
Swimming laps, moderate effort	0.053
Basketball, game (moderate/ vigorous)	0.060
In-line skating, vigorous	0.091
Tennis, singles	0.060
Frisbee, ultimate (vigorous effort)	0.060
Weight lifting	0.045
Circuit training	0.060

*To determine the approximate number of calories burned, multiply the value in the right column by your total body weight and the number of minutes you engage in the activity. For example, if you weigh 150 pounds and walk briskly for 30 minutes, you will burn about 0.029 150 30 130 calories. The values given here are estimates; due to metabolic differences, some people will burn more or fewer calories than indicated by this table.

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Making Changes in Body Composition, 7

Question: Why can’t I just focus on improving one part of my body, such as getting rid of unwanted fat in one area?

It is impossible to target one area for fat burning

You can strengthen muscles in one area, but not reduce fat

The exact area in which the body will mobilize fat for fuel depends on a number of factors, including genetics

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