FTO and obesity due to melanocortin 4 receptor deficiency: In individuals of European descent, a SNP in the first intron of the fat mass and obesity-associated locus (FTO) on chromosome 16q22.2 emerged from early investigations as very strongly associated with severe and childhood-onset obesity; in populations of European descent, the proportion of attributable risk for common obesity conferred by the high-risk haplotype has been estimated at 22% [39].