Chapter 8 Energy Balance Body Composition and Weight

Chapter 8 Energy Balance, Body Composition, and Weight Management • by • Norman D. Sossong, MD, Ph. D • for NSCC: • NTR 150 – Spring 2008

Energy Balance • Energy balance = the balance in the body between the amount of energy consumed and expended • Energy intake = the caloric or energy content of food provided by the sources of dietary energy: carbohydrates (4 kcal/g), fats (9 kcal/g), proteins (4 kcal/g), and alcohol (7 kcal/g) • Energy output = the use of calories or energy for basic body functions, physical activity, and processing of consumed foods

Energy Balance • Energy equilibrium = a balance of energy intake and output that results in little or no change in weight over time • Positive energy balance = energy intake exceeds energy expenditure, resulting in an increase in body energy stores and weight gain • Negative energy balance = energy intake is lower than energy expenditure, resulting in a depletion of body stores and weight loss

Energy In • Regulation of intake • Hunger • Prompts eating; physiological desire • Satiation • Signals to stop eating • Satiety • Lack of hunger • Appetite • Psychological desire

Energy In: Regulatory Factors

Energy Out: Fuel Uses • Major components of energy expenditure • Resting energy expenditure (REE) • = Basal energy expenditure (BEE) • Energy for basic body functions • Affected by body size, composition, age, gender • Physical activity • Highly variable • Affected by body size, fitness level, type of activity • Thermic effect of food (TEF) • Energy to digest, absorb, metabolize food

Energy Expenditure at Rest Constitutes 60 -75% of total energy expenditure Measured as: Basal Metabolic Rate (BMR) = resting metabolic rate (RMR) Conditions: Lying at rest Just awoke from normal sleep 10 -12 hours since last meal No physical activity in the past 12 -18 hours Note: technically the RMR only requires a 3 to 4 hour waiting period after food or exercise to do the test Result: the RMR is slightly higher than the BMR

Factors that Affect Basal Metabolic Rate (BMR) Lean body mass = the body mass (other than fat) = muscles and organ tissue Generally, lean body mass has more metabolism than fat; hence it contributes more to the BMR

Factors that Affect Basal Metabolic Rate (BMR) Muscle & organ mass Liver Brain Muscles (resting) Heart Kidney The rest 29% 18% 10% 7% 100%

Factors that Affect Basal Metabolic Rate (BMR) Age 2 -3% per decade Lean body mass Body fat Organ function Keeping physically active Slows loss of lean body mass Slows gain of fat → preservation of BMR

Factors that Affect Basal Metabolic Rate (BMR) Gender: BMR of ♀ < ♂ ♀ (female): smaller less lean body mass Menstrual cycle influences: Low point: a week before ovulation High point: Just before menstruation starts

Factors that Affect Basal Metabolic Rate (BMR) • Sleep • 10% ↓ in BMR • ↑ lean body mass → ↑ BMR • (growth spurts, e. g. infancy & adolescence) • Hormones • Thyroid • Norepinephrine • Physical stress

Factors that Affect Basal Metabolic Rate (BMR) • Fever • Environmental temperature • Cold • Hot • Mild ↑ • Much ↑ • Starvation • Genetics

Energy Used in Various Activities 15 -30% of BMR

Energy Used to Process Food = Thermic Effect of Food (TEF) = 10% Peaks about 1 hour after eating Usually gone within 5 hours of eating

Energy Balance

Estimating Energy Expenditure • EER: Estimated Energy Requirement • Predicts total energy expenditure (TEE) • Equations for males and females • Factors for age, weight, height, physical activity • Males: • EER = 662 – 9. 53 x Age (yrs) + PA x [15. 91 x Wt (kg) + 539. 6 x Ht (m)] • PA = 1. 0 Sedentary • 1. 12 Low active • 1. 25 Active • 1. 48 Very active

Estimating Energy Expenditure • EER: Estimated Energy Requirement • Predicts total energy expenditure (TEE) • Equations for males and females • Factors for age, weight, height, physical activity • Females: • EER = 354 – 6. 91 x Age (yrs) + PA x [9. 36 x Wt (kg) + 726 x Ht (m)] • PA = 1. 0 Sedentary • 1. 12 Low active • 1. 27 Active • 1. 45 Very active

Body Composition: Understanding Fatness and Weight • Assessing body weight • Height-weight tables • Body mass index (BMI) • Weight (kg) height 2 (m) • Assessing body fatness • Body fat distribution • Waist circumference

BMI vs Mortality

Waist Circumference • If BMI = 25 – 34. 9 kg/m 2 • Then waist circumference • > 40 inches in men • or • > 35 inches in women • is a sign of increased health risk

When Energy Balance Goes Awry • What are the health risks associated with being overweight?

Risks of Being Overweight

When Energy Balance Goes Awry • Early theories of weight regulation • Fat cell theory • Set point theory • Influences on weight gain and obesity • • • Heredity and genetic factors Sociocultural influences Age and lifestyle factors Gender and ethnicity Socioeconomic factors Psychological factors

Sociocultural Influences on Obesity

Gender Biases Regarding Body Shape

Weight Management • Perception of weight • Setting realistic goals • Weight management lifestyle • Diet and eating habits • • Reduce total calories Reduce fat calories Increase complex carbohydrates Improve eating habits • Increase physical activity • Stress management • Self-acceptance

Weight Management • Weight management approaches • Self-help books and manuals • Watch for signs of a fad diet • • • Self-help groups Commercial programs Professional counselors Prescription drugs OTC drugs and dietary supplements

Weight Management • Weight management approaches • Surgery

Underweight • Definition • BMI < 18. 5 kg/m 2 • Causes • Illness • Eating disorders • Metabolic factors • Weight-gain strategies • Small, frequent meals • Fluids between meals • High-calorie foods and beverages