Energy Expenditure (kcal/d)
3500 3000
Resting Energy Expenditure
2500
2000
1500
**
1000
500
0
Before After Predicted
*P<0.05 vs before weight loss
Amatruda et al. J. Clin Invest 1993;92:1236.
1 million
Change in body fat (lb/y)
Energy
Energy Expenditure (%REE)
Weight (% Body Weight)
40
40
20
20
0
Liver, Brain, Kidneys, Gut, Heart
Skeletal Muscle
REE = Resting energy expenditure
Adipose Tissue, Lean Person
Energy Metabolism in Lean and Obese Subjects
3000
Lean (BMI=21 kg/m2)
Obese (BMI=38 kg/m2)
*
2000
*
1000
0 Resting Energy Expenditure
*P<0.05 vs lean subjects
Ravussin et al. Am J Clin Nutr 1982;35:566.
Total Energy Expenditure
* *
Before After Predicted
Regulation of Food IntakeBrain源自Central Signals
Stimulate
NPY Orexin-A AGRP dynorphin galanin
Inibit
α-MSH CART
Muscle glycogen = 2500 kcal
Adipose tissue triglyceride = 120,000 kcal
Obesity Is Caused by Long-Term Positive Energy Balance
Fat Stores
Components of Daily Energy Expenditure
Adipose tissue Adrenal glands
External factors
Emotions Food characteristics Lifestyle behaviors Environmental cues
Food Intake
Lifetime Food Intake
Water 45,300 kg
*
500
0
Reported Actual
*P<0.05 vs reported.
Lichtman et al. N Engl J Med 1992;327:1893.
Reported Actual
Energy Metabolism Before and After Weight Loss Mean BMI Reduced from 31 to 23 kg/m2
0
Adipose Tissue, Obese Person
Relationship Between Resting Energy Expenditure and Fat-free Mass
3000
Lean females Obese females
Lean males Obese males
2000
Principles of Energy Metabolism
Body Energy Stores of Lean 70-kg Man
Liver triglyceride = 450 kcal Liver glycogen = 400 kcal
Muscle triglyceride = 3000 kcal
Segal KR et al. Am J Clin Nutr. 1984;40:995-1000.
Relationship between Tissue Energy Expenditure and Mass
80
Tissue energy expenditure
80
Tissue weight
60
60
REE (kcal/24 h)
1000
0 0 30 40 50 60 70 80 90 100
Fat-Free Mass (kg)
REE = Resting energy expenditure
Owen. Mayo Clin Proc 1988;63:503.
Energy Expenditure (k/cal/d)
Fat 2300 kg 21 kcal*
Cholesterol
8000 kg 31 kcal*
Protein 1900 kg 7 kcal*
*kcal in millions
Cumulative Effect of Small Daily Imbalances in Energy Intake on Body Fat Mass
Total Energy Expenditure
Discrepancy Between Reported and Actual Energy Intake and Expenditure
3000 2500
Energy Intake
*
Energy Expenditure
2000
Kcal/d
1500
1000
CRH/UCN NE
GLP-I
5-HT
Peripheral signals
Glucose

CCK, GLP-1, Apo-A-IV
Vagal afferents
Insulin
+ Ghrelin
Leptin
+ Cortisol
Peripheral organs
Gastrointestinal tract
Thermic effect of feeding
Energy expenditure of physical activity
Resting energy expenditure
8% 17%
8% 32%
75%
60%
Sedentary Person (1800 kcal/d)
Physically Active Person (2200 kcal/d)