Evidence Level
Moderate
BCAAs are perhaps the most over-marketed supplement in sports nutrition. While leucine is genuinely a powerful mTOR activator, the critical insight from Wolfe (2017) is that isolated BCAAs cannot maximally stimulate muscle protein synthesis because they lack the other 6 essential amino acids needed as building blocks. Any complete protein source (whey, meat, eggs) or EAA supplement already contains BCAAs in optimal ratios. The scenarios where BCAA supplementation adds value are narrow: fasted training, very low protein diets, or endurance exercise where complete protein is impractical. For the vast majority of athletes consuming adequate protein, BCAAs are an unnecessary expense.