Applied Nutrition Critical Mass Lean Mass Gainz is one of the best weight gain supplements ever. It consists of a very powerful formula more than any other product to gain weight and muscle. Each serving of the product contains 42 grams of fast and slow absorption protein to supply the body with the protein needed to build muscle for the longest possible period, thus ensuring Muscle growth and restoration for a long time, in addition to the amount of calories that help to increase both weight and muscle and compensate for the body’s lack of energy.