TCF7L2 and type 2 diabetes mellitus: In sum, a diet rich in WGs and fibers seems to decrease fasting insulin independently of genetic variation and to have a protective effect against the onset of T2D, especially in subjects carrying the risk-free alleles of TCF7L2. However, it is likely that the generally inconsistent results observed are attributable to a predominance of study samples composed mainly of European ethnicities, with a concomitant underrepresentation of other ethnicities, which may influence the frequencies of variants associated with T2D and the resulting interactions with dietary factors.