Effects of weight loss on leptin, sex hormones, and measures of adiposity in obese children

Adipose tissue influences steroid conversion by paracrine and autocrine mec hanisms. Leptin is secreted by adipocytes and influenced by sex hormones an d adiposity. Short-term weight loss in the treatment of childhood obesity r educes leptin and adipose tissue. We therefore asked, Do alterations in sex hormones occur owing to weight loss? and can these alterations be explaine d by changes in fat mass or sc fat and are alterations in sex hormones dire ctly related to the fall in leptin? Twenty obese boys and 40 obese girls we re studied before and after 3 wk of low-calorie diet and physical activity. The weight loss program significantly lowered fat mass, abdominal fat dist ribution, sc fat tall p < 0.0001), leptin, insulin, and estradiol tall p < 0.0001) but not testosterone. Changes in leptin were related to changes in body mass and to changes in fat mass in boys. In girls, changes in leptin w ere related to changes in sc fatness and also to changes in insulin. In boy s, the reduction in sc fat was positively correlated to changes in testoste rone (r = 0.54; p <less than> 0.01) and inversely related to the fall in es tradiol (r = -0.41; p < 0.05), In girls, changes in testosterone (r = 0.33; p < 0.05) and in estradiol (r = 0.40; p < 0.01) were related to changes in insulin. Stepwise regression showed that initial leptin was the best deter minant for the fall in leptin (adjusted R-2 = 0;87; P < 0.0001). The result s show that alterations in sex hormones are related to changes in certain f at depots in boys whereas in girls changes in insulin might participate in changes in sex hormones. A greater fall in leptin owing to shortterm weight loss is not associated with greater alterations in sex hormones and initia l leptin is the best determinant to explain the variability in changes in l eptin. The possibility of sex differences in changes in sex hormones second ary to the reduction in fatness warrants further study.