Energy Balance and Body Composition Chapter 8

Chapter 8 Objectives Describe energy balance and the consequences of not being in balance. Discuss some of the physical, emotional, and environmental influences on food intake. List the components of energy expenditure and factors that might influence each. Explain the basal metabolic rate and the factors that affect it. Discuss the role of physical activity in balancing the energy budget. Use equations and tables to determine energy requirements. Distinguish between body weight and body composition, including methods to assess each. Define healthy body weight. Explain the methods used to assess body composition, including BMI and waist circumference. Identify relationships between body weight and chronic diseases. Identify the health risks for underweight. Discuss the health risks for overweight, including heart disease, diabetes, and cancer. Compare and contrast the diagnoses, characteristics, and treatments of the different eating disorders. Identify eating disorders in the athlete including the female athlete triad and disordered eating. Discuss the characteristics and the treatment of the eating disorders anorexia nervosa and bulimia nervosa.

Energy Balance Excess energy is stored as fat Healthy-weight person’s fat stores = 50,000 to 200,000 kcalories! Energy balance: energy in = energy out A shift in balance causes weight changes Not simply fat changes 1 pound of fat = 3500 kcalories

Energy In: Food Intake Hunger Satiation – stop eating Physiological response to nerve signals and chemical messengers Hypothalamus Influences Satiation – stop eating Satiety – not to start eating again

Hunger, Satiation, and Satiety

Energy In: Food Intake Overriding hunger and satiety External cues Boredom, anxiety, stress External cues Time of day, availability, sight, taste of food Environmental influences Cognitive influences Disordered eating

Energy In: Food Intake Sustaining satiation and satiety Nutrient composition Protein is most satiating Low-energy density High-fiber foods High-fat foods – strong satiety signals

Energy In: Food Intake The hypothalamus Control center for eating Integrates messages Energy intake, expenditure, storage Gastrointestinal hormones

Energy Out Components of Energy Expenditure: Basal Metabolism Physical Activity Thermic Effect of Food (TEF) Adaptive Thermogenesis

Energy Out: Basal Metabolism About 2/3 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)

Factors that Affect the BMR

Energy Out: Physical Activity Voluntary movement of skeletal muscles Most variable component of energy expenditure Amount of energy needed Muscle mass Body weight Activity Frequency, intensity, and duration

Energy Out: Thermic Effect of Food Acceleration of GI tract functioning in response to food presence Releases heat Approximately 10 percent of energy intake High-protein foods vs. high-fat foods Meal consumption time frame

Energy Out: Adaptive Thermogenesis Adapt to dramatically changing circumstances Examples Extra work done by body Amount expended is extremely variable Not included in energy requirement calculations

Components of Energy Expenditure

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

Body Weight and Body Composition Body weight = fat + lean tissue (incl water) Ideal Body Weight: Fashion vs Health Not appearance based Perceived body image and actual body size Damaging behaviors Subjective Little in common with health

Defining Healthy Body Weight Body mass index Relative weight for height BMI = weight (kg) height (m)2 Health-related classifications Healthy weight: BMI = 18.5 to 24.9 Underweight, overweight, obese Not a measure of body composition Overweight vs overfat

Body Mass Index (BMI)

BMI and Body Shapes

Distribution of Body Weights in US 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

Body Fat Percentage and Body Shapes

Body Fat and Its Distribution Needing less body fat Needing more body fat Fat distribution Visceral fat Central obesity Subcutaneous fat

“Apple” and “Pear” Body Shapes Compared

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 More precise measures

Common Methods Used to Assess Body Fat

Health Risks Associated with Body Weight & Body Fat Body weight and fat distribution correlate with disease risk and life expectancy Correlations are not causes Risks associated with being underweight Fighting against wasting diseases Menstrual irregularities and infertility Osteoporosis and bone fractures

BMI and Mortality

Health Risks Associated with Body Weight & Body Fat Body weight and fat distribution correlate with disease risk and life expectancy Correlations are not causes Risks associated with being underweight Fighting against wasting diseases Menstrual irregularities and infertility Osteoporosis and bone fractures

Health Risks Associated with Body Weight & Body Fat Risks associated with being overweight Obesity is a designated disease Health risks More likely to be disabled in later years Costs Money Lives Yo-yo dieting

Health Risks Associated with Body Weight & Body Fat Cardiovascular disease Elevated blood cholesterol & hypertension Central obesity Diabetes – type II Weight gains and body weight Cancer Relationship is not fully understood

Health Risks Associated with Body Weight & Body Fat Inflammation & metabolic syndrome Change in body’s metabolism Cluster of symptoms Fat accumulation Inflammation Elevated blood lipids Promote inflammation Fit and fat versus sedentary and slim

Eating Disorders Highlight 8

Eating Disorders Three disorders and prevalence Causes Sociological, psychological, neurochemical Athletes are among most likely Disorder Women Men Anorexia Nervosa 0.9% 0.3% Bulimia Nervosa 1.5% 0.5% Binge Eating Disorder 3.5% 2%

Female Athlete Triad Disordered eating Amenorrhea Osteoporosis Unsuitable weight standards Body composition differences Risk factors for eating disorders in athletes Amenorrhea 2-5% vs 66% Osteoporosis Stress fractures

Female Athlete Triad

Other Dangerous Practices of Athletes Muscle dysmorphia High-protein diets, supplements, weight train for hours, abuse steroids Similar to other distorted body images Food deprivation and dehydration practices Impair physical performance Reduce muscle strength Decrease anaerobic power Reduce endurance capacity

Anorexia Nervosa Distorted body image, denial, need for control Protein-energy malnutrition (PEM) Similar to marasmus Impacts brain function and judgment Causes lethargy, confusion, and delirium Growth ceases, normal development falters Changes in heart size and strength Loss brain tissue, impaired immune response, anemia, GI tract deterioration

Anorexia Nervosa Treatment After recovery Multidisciplinary approach Food and weight issues Relationship issues After recovery Energy intakes and eating behaviors may not return to normal High mortality rate among psychiatric disorders

Bulimia Nervosa Distinct, more prevalent than anorexia Secretive, not as physically apparent Close to ideal weight Single white female, well-educated Binge-purge cycle: lack of control Binge for emotional comfort Cannot stop, done in secret Purge Shame and guilt

Bulimia Nervosa Physical consequences of binge-purge cycle Compromised immune system, fluid/electrolyte imbalances Tooth erosion, red eyes, calloused hands Awareness of abnormality Clinical depression and substance abuse rates are high Treatment Learn to eat three meals a day plus snacks Interdisciplinary team

Binge-Eating Disorder Periodic binging Compared to bulimia nervosa Typically no purging, less restrictive dieting Emotional side is similar Health risks greater than those of obese people who do not binge Behavioral disorder responsive to treatment

Eating Disorders in Society Society plays central role in eating disorders Known only in developed nations More prevalent as wealth increases Food becomes plentiful Body dissatisfaction Characteristics of disordered eating