In recent years, the emergence of drugs that are based on incretins (a group of gut hormones increasing insulin secretion and stimulating a decay in blood glucose levels), such as those acting as glucagon-like peptide-1 (GLP-1) and glucose-dependent insulinotropic peptide (GIP) agonists, has marked an unprecedented success in the treatment of obesity. Here, GIP is linked to obesity due to melanocortin 4 receptor deficiency.