TCF7L2 and type 2 diabetes mellitus: While genetic variants such as  TBC1D4 and TCF7L2 result in up to 50% increased risk of type 2 diabetes by diminishing the incretin effect and impairing glucagon-like peptide 1–induced insulin secretion, a fiber-rich diet may stimulate glucagon-like peptide 1 and mitigate this genetic risk [38, 40].