Among those GWAS findings, the first obesity susceptibility locus identified was the FTO gene, which has the largest effect on obesity risk to date; each additional risk allele in FTO was shown to be associated with a 1- to 1.5-kg increase in body weight and a 20 % to 30 % increase in obesity risk [11, 12]. This evidence concerns the gene FTO and obesity due to melanocortin 4 receptor deficiency.