The complexity of the “obesity problem” has become clearer since adipose tissues have been recognized as an endocrine organ that produces biologically active substances defined as “adipokines,” protein hormones with pleiotropic functions in the regulation of energy metabolism as well as in appetite, insulin sensitivity, inflammation, atherosclerosis, and proliferation [18, 19]. The gene discussed is INS; the disease is obesity due to melanocortin 4 receptor deficiency.