Mice deficient in the prepro-MCH (Pmch) gene (MCH-knockout or MCH-KO mice) are hyperactive, hypophagic, and lean, and are also protected from high fat diet (HFD)-induced obesity, while overexpression of Pmch induces obesity and insulin resistance [7–10]. Here, PMCH is linked to obesity due to melanocortin 4 receptor deficiency.