Branched Chain Amino Acids (BCAAs) are essential amino acids that must be consumed from the diet as they can not be produced by the body. BCAAs are important for bodybuilders as they make up a large percentage of the amino acids found in muscle composition. Branched Chain Amino Acids (BCAAs) are essential amino acids that must be consumed from the diet as they can not be produced by the body. BCAAs are important for bodybuilders as they make up a large percentage of the amino acids found in muscle composition.