Therefore, the purpose of this study was twofold: first, to determine the effect of changes of total, trunk, and nontrunk fat, on total leptin and sOB-r concentrations, and the free leptin index following 6 months of a lifestyle weight loss intervention in obese males and females; second, to identify a regression model for males and females undergoing a diet and physical activity lifestyle intervention that predicts the free leptin index through commonly available indices of obesity. The gene discussed is LEP; the disease is obesity due to melanocortin 4 receptor deficiency.