Energy Balance. Susan Algert. Indirect calorimetry. Measuring energy use without measuring heat production O2 uptake and CO2 output Doubly labeled water method Gas exchange. Bomb Calorimeter. Energy is released in form of heat when food is burned.
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Energy Balance Susan Algert
Indirect calorimetry • Measuring energy use without measuring heat production • O2 uptake and CO2 output • Doubly labeled water method • Gas exchange
Bomb Calorimeter • Energy is released in form of heat when food is burned. • The amount of heat generated provides a direct measure of the amount of energy stored in the food’s chemical bonds. • Direct versus indirect calorimetry
Appetite, Hunger, Satiety • Hunger—physiological response to a need for food triggered by chemical messengers in the brain • Appetite-response to sight, smell, taste of food that initiates or delays eating • Satiety—The feeling of satisfaction that occurs after a meal
Factors influencing eating • Physiological • Sensory • Cognitive • Postingestive and Postabsorptive influences
Components of Energy Expenditure • Basal Metabolism • Physical Activity • Thermic Effect of Food • Adaptive Thermogenesis
Factors that Affect BMR-increase or decrease? • Age • Height • Growth • Body Composition • Fever • Stresses
Resting Energy Expenditure • Harris Benedict equation used to calculate REE based on person’s age, weight, height and sex.
Energy Expenditure of Organs in adult • Brain—19% of REE • Liver—29% of REE • Heart—10% of REE • Skeletal Muscles—18% of REE
Factors that affect BMR • Environmental temperature • Fasting/starvation • Malnutrition • Hormones • Smoking • Caffeine • Sleep
Healthy Body Weight • Tables • BMI • Overweight • Underweight • Body composition
Assessing Body Fat • Densiometry such as underwater weighing • Dual energy x-ray absorptiometry • Skinfold thickness • Bioelectrical impedance analysis • CT and MRI
Health Risks Associated with Body Weight • Hypertension • Heart Disease and Stroke • Diabetes • Cancer • Sleep Apnea • Osteoarthritis • Gout
Current Thinking on Obesity • Obesity gene codes for protein leptin • Produced by fat cells • Leptin acts as a hormone • Promotes negative energy balance
White versus Brown Adipose Tissue • White adipose tissue stores fat for other cells to use for energy • Brown adipose tissue releases stored energy as heat
Neuropeptide Y • Neurotransmitter produced in the brain • Stimulates appetite • Diminishes energy expenditure • Increases fat storage
Dietary fat promotes obesity because • It is palatable • It produces little satiety • It provides 9 kcals per gram • Increases body fat stores in excess
Components of successful weight loss • Low fat diet; cut back one fourth to one third on calories • Activity; 250cals/day, 5-6 X/wk • Behavior Modification including food records • Be realistic
Drugs and Surgery for Obesity • Prescription • Over the counter • Surgery
Weight Gain • Takes time • Eat energy dense foods • Eat snacks • Exercise to eat and gain muscle—strength training and an extra 700-1,000 calories per day