From the remaining 118 studies, studies that examined the modification effect of dietary variables on the association between genetic risk score, instead of TCF7L2, on glycemic parameters (n = 14), and studies investigated the modification effects of dietary variables on the association between TCF7L2 and T2DM but reported no data on glycemic parameters (n = 67) were excluded. The gene discussed is TCF7L2; the disease is type 2 diabetes mellitus.