In agreement with these results, we also found a consistent statistically significant interaction between the FTO rs9939609 polymorphism and leisure time physical activity in determining BMI, waist circumference and obesity prevalence, so that the association between the FTO-risk allele and higher BMI or obesity prevalence disappeared in active subjects and was increased in magnitude of the effect and clinical significance in subjects with low physical activity. This evidence concerns the gene FTO and obesity due to melanocortin 4 receptor deficiency.