One of the strongest associations to obesity was established in 2007, when in a genome‐wide association study (GWAS) for type 2 diabetes, common variants of the FTO gene showed an association with this trait, but subsequent analyses revealed that this association was modulated by body mass index (BMI) (Frayling et al., 2007; Scuteri et al., 2007). This evidence concerns the gene FTO and obesity due to melanocortin 4 receptor deficiency.