Branched-chain amino acids (BCAAs), including the essential amino acids leucine, isoleucine, and valine, have garnered considerable attention due the fact that circulating BCAA levels are positively correlated with a diabetes phenotype (117, 118) and restricting BCAAs have been found to improve health and increase FGF21 (49, 119). This evidence concerns the gene FGF21 and diabetes mellitus.