Weekly subcutaneous injections of glucagon-like peptide-1 (GLP-1) receptor agonists (RAs) or dual GLP-1/glucose-dependent insulinotropic polypeptide (GIP) RAs have been shown to elicit weight reductions of up to 15–20% in adults with obesity or overweight (2, 3) – levels of weight loss previously reported only after bariatric surgery. The gene discussed is GIP; the disease is obesity due to melanocortin 4 receptor deficiency.