Claussnitzer et al. not only showed that the intronic BMI-associated FTO SNP maps within an enhancer element for ARID5B, but could also demonstrate that ARID5B regulates the expression of IRX3 and IRX5, which finally affect adipogenesis, lipid accumulation and thermogenesis [16].This study impressively demonstrated that comprehensive and well-designed functional studies are essential to elucidate molecular pathways underlying the observed associations of genetic loci with obesity. This evidence concerns the gene FTO and obesity due to melanocortin 4 receptor deficiency.