LEP and obesity due to melanocortin 4 receptor deficiency: Although it has not explicitly shown specific loci associated with BMI or obesity, one of the strongest candidates was the FTO alpha-ketoglutarate dependent dioxygenase (FTO) locus along with uncoupling protein 1 (UCP1), leptin (LEP), insulin-like growth factor 1 (IGF-I), scavenger receptor class B member 1 (SCARB1), and insulin receptor substrate 2 (IRS2).