The recent "obesity epidemic" among children and adolescents is a major public health concern. The mechanisms responsible for the increased incidence of childhood obesity are not yet well understood. The absence of a clear mechanism makes treating the obese child or adolescent a difficult task, and standardized therapeutic approaches simply do not yet exist. Metabolic derangements associated with obesity may contribute to the difficulty in treatment. Observed abnormalities in the growth hormone (GH)-insulin-like growth factor-I (IGF-I) axis in obese adults and the impact of exercise on the GH-IGF-I system are of particular relevance to the growing obese child. In this review, we focus on the interacting mechanisms of diet and exercise through specific hormonal mediators and their contribution to the current obesity epidemic. An improved understanding of these mechanisms may be helpful in creating effective treatment programs for children with obesity.