MC4R and obesity due to melanocortin 4 receptor deficiency: In general, obesity is a result of imbalanced energy homeostasis, but genome-wide association studies have identified many single nucleotide polymorphisms (SNPs) in the fat mass and obesity-associated (FTO) gene, melanocortin-4 receptor (MC4R) gene, and other genes [8,9] that are associated with the risk of developing obesity.