Energy Balance Susan Algert Indirect calorimetry Measuring energy use without measuring heat...
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Transcript of Energy Balance Susan Algert Indirect calorimetry Measuring energy use without measuring heat...
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