Building muscle is an anabolic process that is calorie dependent. If you’re not eating enough total calories each day to meet your metabolic needs, you will never build muscle. For athletes with a fast metabolism or hard gainers who just can’t gain weight no matter how much they eat, we engineered MASS FUSION® 2.0. Each serving contains 950 clean calories and three different protein sources: 100% whey protein isolate, whey protein concentrate and micellar casein. Each of these protein sources is absorbed by your body at a different rate, allowing you to avoid slipping into a catabolic state and losing mass.