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 ,000 calories per day