IGF1 and obesity due to melanocortin 4 receptor deficiency: On the other hand, a high protein supply at infancy that exceeds the metabolic requirements would increase plasma and tissue concentrations of insulinogenic amino acids, the growth mediators insulin and insulin-like growth factor-1 (IGF-1), and induce a higher infant weight gain and body fat deposition as well as an increased long-term risk of obesity [34].