HCRT and obesity due to melanocortin 4 receptor deficiency: González et al. observed that activity of orexinergic neurons is suppressed by the act of eating, i.e., the activity of these neurons is reduced during feeding regardless of the kind of food consumed by the laboratory animals, and complete lack of orexin signaling, e.g., in orexin knockout mice, leads to massive overeating and obesity [21].