9. Energy Balance and Body Composition.pdf

Energy Balance and Body Composition  Energy Balance Excess energy stored as fat – Fat used for energy between meals Energy balance: energy in = energy out – A shift in balance causes weight changes Fat, fluid, and muscle tissue – 1 pound of fat = 3500 excess kc...

Energy Balance and Body Composition  Energy Balance Excess energy stored as fat – Fat used for energy between meals Energy balance: energy in = energy out – A shift in balance causes weight changes Fat, fluid, and muscle tissue – 1 pound of fat = 3500 excess kcalories  Energy In: The kCalories Foods Provide Bomb calorimeter – Used to measure a food’s energy value Amount of oxygen consumed – Indirect measure of released energy Calculate energy – From carbohydrate, fat, and protein in food  Food Intake Hunger – Physiological response to nerve signals and chemical messengers Hypothalamus Satiation – feeling of fullness – Message: stop eating Satiety – Message: do not start eating again  Food Intake Overriding hunger and satiety – Stress eating External cues – Time of day, availability, and sight or taste of food Environmental influences – Examples: large portion sizes, favorite foods  Food Intake Sustaining satiation and satiety – Nutrient composition Protein is most satiating Low-energy density foods are more satiating High-fiber foods are more satiating High-fat foods – strong satiety signals  Energy Out: The kCalories the Body Expends Thermogenesis – Generation of heat Categories of thermogenesis – Basal metabolism – Physical activity – Food consumption  Components of Energy Expenditure Basal metabolism – About two-thirds of energy expended in a day Basal metabolic rate (BMR) – Varies from person to person and throughout the day – Lean tissue more metabolically active than body fat Resting metabolic rate (RMR)  Components of Energy Expenditure Physical activity – Voluntary movement of skeletal muscles – Most variable component of energy expenditure Factors influencing energy expenditure – Muscle mass – Body weight – Activity frequency, intensity, and duration Components of Energy Expenditure Thermic effect of food – Acceleration of GI activity in response to food presence – Releases heat – Approximately 10 percent of energy intake – Greater for high-protein foods than high-fat foods – Small in comparison with estimated errors in computing energy output  Estimating Energy Requirements Factors influencing BMR – Gender – Growth – Age BMR declines during adulthood – Physical activity – Body composition and body size Height and weight  Body Weight and Body Composition Defining healthy body weight – Perceived body image vs. actual body size – Standards defining “ideal” Subjective Little in common with health  Defining Healthy Body Weight Body mass index (BMI) – Weight divided by the square of height In kilograms and meters or pounds and inches – Healthy BMI = 18.5 to 24.9 – Obesity-related diseases Evident for BMI greater than 25 Defining Healthy Body Weight  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 Athletes – 7-16% for young men – 15-22% for young women  Body Fat and Its Distribution Fat distribution – Central obesity Visceral fat stored around abdomen – Subcutaneous fat Waist circumference – Good indicator of central obesity Upper body fat more common in men Lower body fat more common in women  Fat Percentage Thin Normal Overweight Obese Men < 10% 10-19% 20-24% ≥ 25% Women < 20% 20-29% 30-34% ≥ 35%  Body Fat and Its Distribution Other measures for body composition – Waist-to-hip ratio – More precise measures  Health Risks Associated with Body Weight and 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 and Body Fat  Health Risks Associated with Body Weight and Body Fat Risks associated with being overweight – Obesity is a designated disease Health risks – More likely to be disabled in later years – Costs Money due to lost work Life expectancy  Health Risks Associated with Body Weight and Body Fat Cardiovascular disease – Strong relationship to central obesity – Elevated blood cholesterol and hypertension Diabetes – Type 2 – Three times more likely to develop in obese person Inflammation and the metabolic syndrome Cancer – Relationship not fully understood Fit and Fat versus Sedentary and Slim Cardiorespiratory and muscular fitness – Play important role in health and longevity Independent of body weight Fitness offers many health benefits