Mice lacking NPY neurons develop obesity and hyperinsulinemia in response to a normal chow diet, but exhibit reduced weight gain and abnormal improvement in glucose tolerance under a high-fat diet (Joly-Amado et al., 2012; Vahatalo et al., 2015), pointing to the role of NPY/AgRP neurons in coordinating nutrient distribution. This evidence concerns the gene NPY and obesity due to melanocortin 4 receptor deficiency.