FTO and obesity due to melanocortin 4 receptor deficiency: Recent studies have revealed a strong association between common variants in introductory studies on the FTO gene and obesity in children and adults.2-4 Frayling and co-workers found that each rs9939609 allele (chr16:52,378,028; dbSNP build 129) increased body weight by 1.2 kg in the general adult population and conferred a 31% higher risk of developing obesity.5