IGF1 and obesity due to melanocortin 4 receptor deficiency: The most common hypothesis explaining these associations between higher animal protein intake and obesity is the effects of amino acids, especially branched-chained amino acids (BCAA) in addition to other amino acids like arginine [8], assumed to stimulate insulin and insulin-like growth factor 1 (IGF-I) secretion as well as affect preadipocyte metabolism leading to overweight in children [9].