Various genes have been identified related to obesity, such as mutation in melanocortin 4 receptor gene, the single nucleotide polymorphism on the fat mass and obesity-associated gene, defects in leptin, leptin receptor, proopiomelanocortin, and proprotein convertase [30,33], but although genetic defects increase individual susceptibility to obesity, they explain for less than 1% of the cases [34]. The gene discussed is LEP; the disease is obesity due to melanocortin 4 receptor deficiency.