FTO and obesity due to melanocortin 4 receptor deficiency: Another example of this is with the refinement of the TCF7L2 association with type 2 diabetes129 down to a single, presumably causative, SNP working with a West African patient cohort.130 With respect to BMI and obesity, the role of the FTO locus in populations of African ancestry was initially less obvious;108,131 however, from large cohort studies109,110 it is becoming increasingly clear that rs3751812 allele is a good proxy for the underlying association in Africans and Caucasians.