FTO and obesity due to melanocortin 4 receptor deficiency: Frayling et al. was the first to identify the rs9939609 on intron 1 as an obesity risk SNP, which was found to be in high linkage disequilibrium (LD) (r2 > 0.5) with a region spanning 47 kb including intron 1, 2 and exon 2 of the FTO gene [21].