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