The importance of the incretin effect in the pathogenesis of T2D and obesity is highlighted by the fact that exogenous administration of drugs that mimic endogenous GLP-1 actions, namely GLP-1 receptor agonists (GLP-1 RAs), has the ability to lower blood glucose levels and promote weight reduction by correcting multiple pathophysiological abnormalities of the two entities [12]. The gene discussed is GLP1R; the disease is obesity due to melanocortin 4 receptor deficiency.