BACKGROUND: Little is known about the effects of physical training on plasma leptin concentrations in children. OBJECTIVE: We sought to determine the effects of 4-mo periods with and without physical training on leptin in obese children and to explore the determinants of leptin at baseline and in response to physical training. DESIGN: Participants were 34 obese 7 to 11-y-old children randomly assigned to engage in physical training during either the first or second 4 mo of the 8-mo study. RESULTS: Total body composition, visceral adiposity, and insulin were all positively correlated with leptin at baseline (p <= 0.05); however, only fat mass was retained in the final stepwise regression (p = 0.0001, R2 = 0.57). Leptin decreased during the 4-mo periods of physical training and increased in the 4 mo after cessation of physical training (p < 0.001 for the time by group interaction). Decreases in leptin were greatest in children with higher pretraining leptin concentrations, those whose total mass increased least, and those whose insulin concentrations decreased most (p <= 0.05); only pretraining leptin concentration (p = 0.009) and change in total mass (p = 0.0002) were retained in the final regression (R2 = 0.53). CONCLUSIONS: In obese children, leptin concentration decreased during 4 mo of physical training and increased during a subsequent 4-mo period without physical training, fat mass was highly correlated with baseline leptin, and greater reductions in leptin during 4 mo of physical training were seen in children with higher pretraining leptin and in those whose total mass increased least.
Copyright by the American Society for Clinical Nutrition.

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