Among them there were many studies [1,23,27-29], including the first GWAs that detected the association between the FTO rs9939609 polymorphism and obesity risk [1], in which such association with type 2 diabetes disappears after adjusting for BMI, leading the authors to conclude that as the association between the FTO polymorphism and type 2 diabetes was mediated by BMI, the FTO is a susceptibility locus for obesity, but not for type 2 diabetes. This evidence concerns the gene FTO and obesity due to melanocortin 4 receptor deficiency.