Branched-chain amino acids (BCAAs) are a group of three essential amino acids: Leucine, Isoleucine and Valine. BCAA supplements are commonly taken in order to boost muscle growth and enhance exercise performance. They can also help with weight loss and reduce fatigue after exercise. BCAAs are considered essential because, unlike non-essential amino acids, your body cannot produce them. Therefore, it is essential to get them from your diet or through supplementation.