Chapter 8

Energy Balance and Body Composition

Energy Balance

• Excess energy is stored as fat• Fat is used for energy between meals

• Energy balance: energy in = energy out• A shift in balance causes weight changes• 1 pound of fat = 3500 kcalories

Energy In: Food Composition

• Direct measure of food’s energy value– Bomb calorimeter

• Indirect measure of energy released– Oxygen consumed

• kCalorie calculations

Energy In: Food Composition

• Appetite prompts a person to eat or not eat

• Hunger- An irritating feeling that prompts thoughts of food and motivates one to start eating

• Satiation – tells us to stop eating

• Satiety – tells us not to start eating again

Energy In: Food Composition

Energy In: Food Composition

• Overriding hunger and satiety• Stress eating

• External cues• Time of day, availability, sight, taste of food

• Environmental influences• Examples

• Disordered eating

Energy In: Food Composition

• Sustaining satiation and satiety• Nutrient composition• Protein. low-energy density foods, high-fiber foods, is most

satiating• High-fat foods – stimulate appetite• Complex carbs are satiating promoting

Energy In: Food Composition

• The Hypothalamus• Control center for eating• Integrates messages• Energy intake, expenditure, storage

• Gastrointestinal hormones

Energy Out

• Thermogenesis • Basal metabolism• Physical activity• Food consumption• Adaptation

Components of Energy Expenditure

• Basal Metabolism• About two-thirds of energy expended in a day• Metabolic activities• All basic processes of life• Basal metabolic rate (BMR)

• Variations• Weight• Lean tissue

• Resting metabolic rate (RMR)

Components of Energy Expenditure

• Physical Activity• Voluntary movement of skeletal muscles

• Most variable & changeable component of energy expenditure

• Amount of energy needed depends on a few factors

Components of Energy Expenditure

• Thermic Effect of Food• Acceleration of GI tract functioning in response to food

presence

• Approximately 10 percent of energy intake

• High-protein foods vs. high-fat foods

• Meal consumption time frame

Components of Energy Expenditure

• Adaptive Thermogenesis• Adapt to dramatically changing circumstances• Extra work done by body• Amount expended is extremely variable & specific to

individuals• Not included in energy requirement calculations

Estimating Energy Requirements

• Gender• BMR

• Growth• Groups with adjusted energy requirements

• Age• Changes with age

• Physical activity• Levels of intensity for each gender

• Body composition & body size• Height• Weight

Defining Healthy Body Weight

• Ideal• Not appearance based• Subjective• Little in common with health

• Body mass index• Relative weight for height• BMI = weight (kg)

height (m)2

• Health-related classifications• Healthy weight: BMI = 18.5 to 24.9• Other classifications

• Not a measure of body composition • Variations

Distribution of body weights in U.S. Adults

Body Fat and Its Distribution

• Important information for disease risk• How much of weight is fat?• Where is fat located?

• Ideal amount of body fat depends on person

• General disease risk levels• Young men: 22%; Men over 40: 25%• Young women: 32%; Women over 40: 35%

Body Fat and Its Distribution

• Needing less body fat• Needing more body fat• Fat distribution• Visceral fat• Central obesity

• Subcutaneous fat

Body Fat and Its Distribution

• Waist circumference • Indicator of fat distribution & central obesity• Women: greater than 35 inches• Men: greater than 40 inches

• Waist-to-hip ratio

Other techniques for body composition

Health Risks w/ Body Wt & Fat

• Body weight and fat distribution correlate with disease risk and life expectancy

• Risks associated with being underweight• Fighting against wasting diseases• Menstrual irregularities and infertility• Osteoporosis and bone fractures• Cannot handle medical stresses.• Pregnancy problems.

• Risks associated with being overweight• Obesity is a designated disease• More likely to be disabled in later years• Costs• Yo-yo dieting

Health Risks w/ Body Wt & Fat

• Cardiovascular disease• Elevated blood cholesterol & hypertension• Central obesity

• Diabetes – type II• Central obesity• Insulin resistance• Weight gains and body weight

• Cancer• Relationship is not fully understood

• Inflammation & metabolic syndrome• Change in body’s metabolism• Fat accumulation• Elevated blood lipids