Without talking about steroids, being a decent size is all about genetics...
People say you have to eat 5000 calories, and 500g protein a day to get big, but I am at my biggest in my life (pretty lean 230, but yeah, i am 6'3). I only eat 3 meals a day. oatmeal in the AM, chicken sandwich at lunch, and dinner (steak and sweat potato, or something along those lines).
Lou Ferrigno was the same way, he only ate 3 meals a day, a far cry from 7000 calories, 400g of pretein etc...
also, look at the silverback gorilla, eats only grass and ants a day with little to no protein and they are huge.
just saying, genetics play a huge role.