CIRCULATING LEPTIN IN NORMAL-CHILDREN AND DURING THE DYNAMIC PHASE OFJUVENILE OBESITY - RELATION TO BODY FATNESS, ENERGY-METABOLISM, CALORIC-INTAKE, AND SEXUAL DIMORPHISM

In 112 obese compared with 42 lean children, we found that serum lepti n is elevated early in the evolution of childhood-onset obesity (28.4 +/- 1.4 vs. 4.5 +/- 0.4 ng/ml in lean children, P < 0.0001) and correl ates with adiposity. Obese children also had higher serum leptin norma lized to fat mass. Despite high serum leptin, obese children ingested 2-3 times more calories than did lean control subjects (P < 0.0001) an d gained weight rapidly (10.2 +/- 0.3 vs. 2.9 +/- 0.1 kg/year in contr ol subjects, P < 0.0001). Girls had higher leptin levels than did boys , in obese as well as in nonobese children, and showed a closer correl ation between adiposity and serum leptin. Elevation of serum leptin wa s comparable before and after puberty in obese boys, but puberty furth er increased leptin levels in obese girls (36 +/- 3 ng/ml), resulting in a clear sexual dimorphism with pubertal obese boys (22 +/- 5 ng/ml, P < 0.005). In conclusion, increased serum leptin reflects but does n ot halt fat deposition in childhood obesity. After normalization to bo dy adiposity, leptin was found to be increased independently by obesit y status, female sex, and female sexual maturation.