Similarly to leptin or leptin receptor deficiency, leptin resistance leads to morbid obesity and interleukin-1 receptor 1 (IL1R1) deficiency and the major receptor mediating the biological function of the IL-1 cytokine family (activates inflammatory signaling pathways) also leads to a higher degree of obesity and metabolic disturbance [218,219,220]. This evidence concerns the gene LEP and obesity due to melanocortin 4 receptor deficiency.