II. The Role of Vitamins, Minerals, and Water for Proper Body Physiology

ch09_lecture_energy_balance.pdf

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Chapter 9: Energy Balance and Weight Management

Student learning outcomes: At the end of this chapter, you should be able to:

Describe how obesity and eating disorders affect health

Discuss how genetics and lifestyle affect body type

Plan a diet to meet calorie recommendations to maintain, gain, or lose weight

THINK about this – then share within a PAIR – then SHARE with the class

Which diseases are associated with obesity?

What is BMI?

Obesity

Excess body fat increases health risks

high blood pressure heart disease high blood cholesterol diabetes gallbladder disease arthritis sleep disorders respiratory problems

menstrual irregularities breast, uterus, prostate, & colon cancer incidence and severity of infectious disease poor wound healing surgical complications

Excess body fat increases health risks

Body mass measurements Lean body mass: mass of non-fat body parts

Body weight = weight of fat + lean body mass

Body mass index (BMI) =

Weight in kilograms/(Height in meters)2

or [Weight in pounds/(Height in inches)2] × 703

Body mass index

Underweight: < 18.5 kg/m2

Overweight: > 25 and < 30 kg/m2

Obesity: > 30 kg/m2

Morbid or extreme obesity: > 40 kg/m2

Percent body fat

Young, healthy female: 21–32% of total weight

Young, healthy male: 8–19% of total weight

With age // Lean body mass decreases // Body fat increases

Measuring body composition

Body fat location

Subcutaneous fat: adipose tissue under the skin, for example, in hips and legs (pear shape)

Visceral fat: adipose tissue around abdominal organs (apple shape)

more metabolically active associated with higher disease risk

Body fat location

Concept check How has the incidence of overweight and obesity changed in the United States over the past few decades?

What are two chronic disorders that are more common in obese individuals than in lean individuals?

When is a high BMI not associated with an increased health risk?

What type of fat increases health risks?

Energy balance

Maintain weight: // calories consumed = calories expended

Weight gain: // calories consumed > calories expended

Weight loss: // calories consumed < calories expended

Appetite vs. hunger

Appetite: desire to consume specific foods triggered by external cues (for example, smell) independent of hunger

Hunger: desire to consume food that is triggered by internal physiological signals

Portion distortion

THINK about this – then share within a PAIR – then SHARE with the class

What are some reasons for increasing obesity rates?

Activity & obesity

Energy intake review

How much energy do each of the following contribute?

carbohydrate: _____ calories/gram

fat: _____ calories/gram

protein: _____ calories/gram

alcohol: _____ calories/gram

Energy intake

Energy expenditure

Total energy expenditure: total amount of energy used by the body each day

Basal metabolism: includes all essential metabolic functions to keep you alive

Basal metabolic rate (BMR): energy expended for basal metabolism

Thermic effect of food (TEF) or diet-induced thermogenesis: energy required for food digestion, absorption, metabolism, storage

Basal metabolism

Thermic effect of food

Physical activity

15–30% of total energy expenditure

Includes:

Planned and daily activities // Walking, yard work, work-related activities, fidgeting

Non-exercise activity thermogenesis (NEAT): energy expended for everything that is not sleeping, eating, or sports-like exercise

Energy balance

Excess calorie review

How does the body store excess calories?

Excess calories

Small amount stored as glycogen in liver and skeletal muscle

Remainder stored as fat in adipocytes

Storage of excess calories

Estimated energy requirements

Estimated energy requirement (EER): number of calories needed for a healthy individual to maintain his or her weight

Calculated based on gender, age, height, weight, activity level, and life stage

Need to know physical activity (PA) value

Physical activity & PA level

Estimated energy requirements

Concept check

Why are more Americans obese today compared to 40 years ago?

What happens to energy stores when energy intake exceeds expenditure?

Which component of energy expenditure is easiest to modify?

What is your EER?

THINK about this – then share within a PAIR – then SHARE with the class

Which has the most influence on obesity?

a) Genetics b) Personal choices c) Socioeconomic class d) Other influences

Physical activity & PA level

Genes & body weight

>100 genes are associated with body weight management

20–30 obesity genes produce proteins affecting how much food you eat, how much energy you expend, and the way fat is stored

Genes vs. environment

Set point Body compensates for diet and exercise variations by adjusting energy intake and expenditure to keep weight at a particular level

Body responds to short-term changes in food intake and activity and long- term changes in stored body fat

Determined in part by genes

Satiety

Feeling of fullness and satisfaction caused by food consumption that eliminates desire to eat

Short-term regulation of food intake

Hormones & weight control

Ghrelin: released by the stomach to stimulate the desire to eat at usual mealtimes

Peptide YY: released by the gastrointestinal tract after a meal in proportion to the number of calories consumed to reduce appetite

Leptin: secreted from adipocytes in proportion to their size to regulate energy intake and expenditure

Leptin

Energy expenditure

Concept check

What is the role of genes in regulating body weight?

Why do we feel hungry at about the same times every day?

What happens to leptin levels when you lose weight?

Why are some of us obese and some of us lean?

Weight management

Balance between energy intake & expenditure

Weight-loss decisions

Losing weight

Eat less, exercise more, or both

Change behaviors that led to weight gain

To lose a pound of fat, decrease intake and/or increase expenditure by about 3500 Calories

To lose a pound in a week, tip energy balance by about 500 Calories/day

Losing weight at a rate of 1/2 – 2 lbs/week helps ensure mostly fat loss and not lean tissue

For most people, a loss of 5% to 15% of body weight will significantly reduce disease risk

Weight cycling or yo-yo dieting

What should I eat?

Balance your intake and output

Cut down on calories

Increase activity

Behavior modification

THINK about this – then share within a PAIR – then SHARE with the class

What could be done to decrease obesity?

From the textbook:

“It has been estimated that a population-wide shift in energy balance of only 100 calories/day, the equivalent of walking a mile or cutting out a scoop of ice cream, would prevent further weight gain in 90% of the population.”

Gaining weight

Have a medical assessment to determine reasons for low weight

Gradually increase energy-dense foods

To encourage muscle gain rather than fat, strength-training exercise should be a component of any weight gain program

Weight-loss diets

Effective programs promote:

weight loss can be maintained over the long term

healthy weight-loss

changes in the lifestyle patterns that led to weight gain

To maintain weight loss, fewer calories need to be consumed

Weight-loss plans

Prescription weight-loss drugs

Reduce appetite by affecting brain neurotransmitters // for example, phentermine, trade name Adipex

Decrease fat absorption in the intestine // for example, orlistat, brand name Xenical

Recommended only if health is seriously compromised by body weight

Disadvantage: weight usually regained when drug is discontinued

Over-the-counter weight loss drug

Weight-loss supplements Not regulated by the FDA

Contain soluble fiber to help feel full

“Fat burners”

Ephedra - increases blood pressure and heart rate and constricts blood vessels (banned in 2004)

Bitter orange, guarana, green tea extract

Weight loss through water loss

Diuretics or laxatives (senna, aloe, buckthorn, rhubarb root, cascara, and castor oil)

Weight-loss surgery

Alter the gastrointestinal tract to reduce food intake and absorption

Adjustable gastric banding: limits amount of food that can be consumed

Gastric bypass: reduces amount of food that can be consumed and absorbed

Liposuction: a large hollow needle is inserted under the skin into a fat deposit to vacuum out the fat = cosmetic

Weight-loss surgery

Debate Is surgery a good solution to obesity?

Abnormal or disordered eating

Psychological illness characterized by specific abnormal eating behaviors, often intended to control weight

Anorexia nervosa: self-starvation, a distorted body image, and abnormally low body weight

Bulimia nervosa: consumption of a large amount of food at one time (binge eating) followed by purging behaviors (self-induced vomiting)

Binge-eating disorder: recurrent episodes of binge eating in the absence of purging behavior

Abnormal or disordered eating

Factors contributing to abnormal or disordered eating

Body ideal & body weight

Anorexia nervosa Desire to be thin causes decreased food intake

Overwhelming fear of gaining weight, even if already underweight

Characterized by: severe weight loss, amenorrhea, constipation, and restlessness

Behaviors: contribute to the maintenance of a body weight that is > 15% below normal

Affects about 1% of US female adolescents

Anorexia nervosa

Bulimia nervosa

Powerful urges to overeat with a morbid fear of becoming fat

Characterized by: intense fear of becoming fat, negative body image, and distorted perception of body size

Behaviors: semi-starvation interrupted by periods of gorging followed by behaviors to eliminate extra calories and prevent weight gain

Bulimia nervosa

Binge-eating disorder

Engage in recurrent binge eating episodes but do not regularly engage in purging behaviors

Most common eating disorder

Binge-eating disorder

Other eating disorders

THINK about this – then share within a PAIR – then SHARE with the class

What could be done to decrease eating disorders?

Concept check Which eating disorder is characterized by extreme weight loss? Which is characterized by excess weight?

What factors contribute to the higher incidence of eating disorders among women than among men?

What is meant by body image?

How does a food binge differ from “normal” overeating?

What is happening in this picture?

Sumo wrestlers train for many hours each day and eat huge quantities of food. The result is a high BMI and a large waist but surprisingly little visceral fat.

Applications

What advice could you give to a loved on about weight loss?

Nutrition in the news

Vending machines in schools

“Fat tax” on high-calorie foods

National health care

Checking student learning outcomes

How do obesity and eating disorders affect health?

How do genetics and lifestyle affect body type?

What advice would you give to a loved one to maintain, gain, or lose weight?