This renewed interest in body composition stems from a new era in GLP1-based pharmacotherapies for obesity, in which a key benchmark of 20% total body weight loss has now been surpassed, for example, in response to the dual incretin (combined GLP1 and Glucose-dependent Insulinotropic Polypeptide [GIP]) agonist, Tirzepatide, in the SURMOUNT-4 randomised clinical trial [87]. The gene discussed is GCG; the disease is obesity due to melanocortin 4 receptor deficiency.