In the arcuate nucleus (ARC) of the hypothalamus, the leptin–melanocortin pathway regulates energy metabolism and appetite through neuropeptide Y (NPY), agouti-related protein (AgRP), pro-opiomelanocortin (POMC), and cocaine- and amphetamine-related transcript (CART), which show altered expression in response to obesity [3,6]. Here, NPY is linked to obesity due to melanocortin 4 receptor deficiency.