In addition, diet-induced obesity in rodents is associated with hyperleptinemia and with impaired LepRb signaling in arcuate neurons, including POMC and AgRP/NPY/GABA cells, supporting the notion that diet-induced defects in LepRb signaling within these neurons may play a primary role in the development of obesity [4,19-21]. This evidence concerns the gene NPY and obesity due to melanocortin 4 receptor deficiency.