The present meta-analysis was based on cross-sectional data and thus does not provide information on the longitudinal relationships between variables. While germline DNA remains stable throughout the life course, PA levels may change and may be confounded by other lifestyle and environmental factors that correlate with PA and body weight. So far, only three prospective follow-up studies (n range = 502 to 15,844) on the interaction between FTO and PA have been reported, and none showed an interaction between FTO and baseline PA, or change in PA, on weight change during follow-up [21]–[23]. Although studies investigating PA alone did not find an interaction, the Diabetes Prevention Program in the US showed an interaction between FTO and a 1-y lifestyle intervention, consisting of PA, diet, and weight loss combined, on change in subcutaneous fat area among 869 individuals [37]. The minor allele of the FTO variant was associated with an increase in subcutaneous fat area in the control group but not in the lifestyle intervention group [37]. Two studies have tested whether FTO modified the effect of a standardized exercise program
