With less than 2g of fat per serving, MuscleMeds Carnivor Mass is the best lean mass gainer you could use. The formula consists of 50g hydrolyzed beef protein isolate and 125g high-impact reactive carbs, and it’s loaded with creatine and BCAAs. The product created using a dual-action insulin signal amplifying technology supports maximum muscle anabolism while minimizing fat storage. Another plus is that this mass gainer is sugar and lactose-free.