NPY and obesity due to melanocortin 4 receptor deficiency: It reaches brain tissue through blood circulation, binds to leptin receptors that feed on the central nervous system, and sends signals to the central nervous system, producing a series of effects: Inhibitory neuropeptide Y (NPY) promotes the combination of melanocorticoid and melanocorticoid receptor 4 and produces the completely opposite effect to S protein, so as to inhibit feeding and the occurrence of obesity, increase the expression of uncoupling protein in adipose tissue, and consume excess energy in the form of heat energy [7].