FTO and obesity due to melanocortin 4 receptor deficiency: Increased DNA methylation on the FTO obesity susceptibility haplotype [15], hypomethylation of FTO in type 2 diabetes cases compared to controls [16] and evidence (although not demonstrating a causal relationship) that the effect of the FTO rs9939609 risk allele may be mediated by methylation changes in other genes [17] have all been described in human peripheral blood DNA.