Muscle Feast branched-chain amino acids (BCAA) is a 4:1:1 ratio of leucine, isoleucine and valine. BCAAs are essential and must be consumed through the diet, since the human body cannot make them. In order to get energy, the body can actually break down muscle to get these BCAAs. Therefore, by supplying them during or after a workout, muscles and other tissues are spared from breakdown, which occurs as a natural part of metabolism.