FTO and obesity due to melanocortin 4 receptor deficiency: Of these, only one known BMI variant, rs1421085 in the FTO gene, was significantly associated with Obesity Class III in the discovery phase [OR=1.45, P = 3.93 X 10-26] and was validated in the replication cohort [OR=1.47, P = 2.11 X 10-14] in this study.