Basal metabolism of obese adolescents: Evidence for energy conservation compared to normal and lean adolescents.

To test if obese adolescents systematically conserve energy, comparisons of basal metabolic rate (BMR) of obese, normal, and lean male and female adolescents were made. Obese had eleevated values by as much as 23% (P ≤ 0.05) expressed as kJ · 24 hr-1 compared to the normal and lean. When indexed to body mass (kJ · kg-BM-1 · hr-1 ), the BMR for the obese was depressed by as much as -53% (P ≤ 0.01), and when indexed to fat free mass (kJ · kg-FFM-1 · hr-1 ) it was depressed by -33% compared to normal and lean adolescents. A "theoretical metabolic rate" (TMR), based on the observed fat free mass, fat mass, and their thermal equivalents, was proposed as a theoretical way to properly index basal metabolism, referenced to body composition. Comparisons of the TMR between the obese, normal, and lean revealed that the obese values were depressed by an average -22% (P ≤ 0.05). In comparison, differences in TMR between the normal and lean males and females were no larger than 8% (ns). It was concluded that since both the observed BMR (expressed relative to body composition), and the derived TMR values were depressed for the obese compared to the normal and lean adolescent, the data suggest an energy saving hypothesis for obese adolescents.