Different hypotheses have been proposed to understand the physiological mechanisms involved in this substantial different: a stronger impact of obesity on insulin sensitivity in youth, although it has been reported that insulin sensitivity is worsen by aging, a major visceral abdominal fat distribution although total body fat is similar, a superior glucotoxic or inflammatory effect induced by IGT in youth in comparison with adults, or the lower level of HDL in adolescents, considering the theory according to which HDL plays a role in inducing glucose disposal through skeletal muscle. The gene discussed is INS; the disease is obesity due to melanocortin 4 receptor deficiency.