In a large European sample of children (n = 4406), the effect of the FTO genotype on BMI was stronger among children with parents of low socioeconomic status.6 In another study, the association between a composite indicator of genetic risk of obesity and BMI was stronger for more recent birth cohorts, who by implication had had greater exposure to the obesogenic environment.7 This evidence concerns the gene FTO and obesity due to melanocortin 4 receptor deficiency.