Energy expenditure during carbohydrate overfeeding in obese and nonobese adolescents.

Basal metabolic rate (BMR), thermic effect of food (TEF), and total daily energy expenditure (TDEE) were measured in six nonobese and seven obese adolescents during periods of weight maintenance and 2 wk of carbohydrate overfeeding. BMR and TEF were measured by indirect calorimetry and TDEE by the doubly labeled water method. Fasting blood levels of insulin, thyroid, and norepinephrine (NE) and urinary excretion of NE and 4-hydroxy-3-methoxymandelic acid (VMA) were measured before and after overfeeding. Energy intake was 1.61 X BMR during maintenance and 2.45 X BMR during overfeeding. BMR increased comparably in both groups during overfeeding (obese, 7.9 +/- 1.2%, nonobese, 8.6 +/- 1.9%). TEF was similar and did not change significantly during overfeeding (maintenance: obese, 9.4 +/- 0.6%; nonobese, 9.8 +/- 0.4% vs. overfeeding: obese, 8.6 +/- 0.3%; nonobese, 9.2 +/- 0.7%). TDEE did not differ significantly between obese and nonobese. Increases in insulin and 3,5,3'-triiodothyronine levels were significant but did not differ between the two groups. Plasma NE and urinary excretion of VMA and NE did not increase during overfeeding. The thermogenic response to food or to overfeeding does not appear reduced in obese adolescents, nor does facultative thermogenesis appear to be a significant factor in weight maintenance in adolescents.