As natabolic said, I think it depends on your definition of mass monster. I knew a guy from high school who hovered around 275-300 through his junior and senior year. He was at about 14-16% bf. He wasn't any genetic elite, but he ate like crazy. I remember him eating a potato chip and peanut butter sandwich because there was nothing else in the house. But he worked his ass off in the gym, plus with football practice his metabolism was running high... He cut down after high school because he broke his back in an accident, and football was no longer an option. He ended up being about 240 at 6% bf and he never touched a supplement besides creatine, protein, and a fat burner. To see him at that weight, he looked big! I have more stories but I believe that if you're talking about close to 300 lbs at 4% bf than yeah I think than AAS may be necessary. But if you're talking about someone like the example I mentioned above, it is totally attainable. It will just take time, and a lot of eating!