In this cross-sectional study, the association of Pro12Ala PPARγ2 polymorphism with obesity, plasma lipids, insulin and leptin concentrations, as well as insulin resistance estimated using the homeostasis model assessment for insulin resistance (HOMA) (Matthews et al., 1985) is investigated in a population-based sample of children in whom the effect of several factors such as sex hormones, alcohol consumption, smoking etc. that may contribute to the discrepancies observed in adults can be avoided. This evidence concerns the gene INS and obesity due to melanocortin 4 receptor deficiency.