In 2007, a genome-wide association study (GWAS) revealed an association between a single nucleotide polymorphism (SNP) in the first intron of the fat-mass-and-obesity-related gene FTO and increased BMI and adiposity.[1] Subjects carrying two copies of the risk allele were, on average, 3 kgs heavier and had a 1.7-fold increased risk for developing obesity.[1] Subsequently, this result has been replicated in various populations and across different age groups (reviewed in [2]). Here, FTO is linked to obesity due to melanocortin 4 receptor deficiency.