FTO and obesity disorder: In contrast, the first study to show an association between FTO and obesity [13], as well as other studies [12,28-31] and a meta-analysis by Kilpelainen et al. [32] (data from previous studies plus analyses of 4 large European birth cohorts), found no inverse association between the FTO risk allele and birth weight or evidence of a positive association by the postnatal age of 2 weeks (12].