EVLUTION NUTRITION LEAN BCAA 237g. During exercise and dieting, muscle protein breakdown, and in particular, BCAA breakdown for energy is increased. Think of BCAAs as protectors for your muscles! LEANBCAA boosts performance and promotes lean muscle growth through 5 grams of pure BCAAs in the most researched and proven 2:1:1 ratio of 2.5 grams Leucine, 1.25 grams Isoleucine and 1.25 grams Valine per serving.