Basal metabolism of obese adolescents: age, gender and body composition effects.

Body composition (percent fat and lean body mass) and basal metabolic rates were determined in 67 obese adolescents ranging in age from 10 to 16 years (30 male, 37 female). Basal oxygen uptake was determined on rising in the morning using open-circuit spirometry with a 10-min collection period. Body composition was determined from body density measurements using the underwater weighing procedure. There were no male-female differences (except for basal VCO2 production, P less than 0.05) for any body composition or metabolic variable. The subjects' (male and female) average weight was 73 kg, height--157 cm, percent fat--40 percent, fat weight--30 kg, lean body mass--92 kg, and kcal/24 h--1535. Correlations between age, body composition and basal energy expenditure were all moderate to low (r less than or equal to 0.78). In contrast to adult data, lean body mass was not highly correlated to basal energy expenditure suggesting that perhaps there is a 'metabolic condition' of the obese adolescent modulated by excess fatness or the instability of the body cell mass. Stepwise multiple linear regression revealed that for the obese male adolescent, body surface area and percent fat, and for the obese female adolescent body surface area and body weight resulted in the best prediction of basal kcal/24 h. The standard errors of prediction were +/- 17.9 percent for the males, and +/- 14.4 percent for the females.