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
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
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
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
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)
Total Energy Expenditure
Discrepancy Between Reported and Actual Energy Intake and Expenditure
3000 2500
Energy Intake
*
Energy Expenditure
2000
Kcal/d
1500
1000
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 Intake
Brain
Central Signals
Stimulate
NPY Orexin-A AGRP dynorphin galanin
Inibit
α-MSH CART
Principles of Energy Metabolism
Body Energy Stores of Lean 70-kg Man
Liver triglyceride = 450 kcal Liver glycogen = 400 kcal
Muscle triglyceride = 3000 kcal
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
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.
0
Adipose Tissue, Obese Person
Relationship Between Resting Energy Expenditure and Fat-free Mass
3000
Lean females Obese females
Lean males Obese males
2000
1 million
Change in body fat (lb/y)
Energy
*
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
Adipose tissue Adrenal glands
Externalቤተ መጻሕፍቲ ባይዱfactors
Emotions Food characteristics Lifestyle behaviors Environmental cues
Food Intake
Lifetime Food Intake
Water 45,300 kg