Polymorphisms in peroxisome proliferator-activated receptor γ (PPARG), adiponectin (ADIPOQ), leptin receptor (LEPR), and insulin receptor substrate 2 (IRS2) have been linked to obesity and type 2 diabetes mellitus (T2D)16–19. The gene discussed is IRS2; the disease is obesity due to melanocortin 4 receptor deficiency.