Diet is overrated. You need protein fat and carbs and lots of 'em all if you want to grow.
I've spoken to hundreds of pros, past and present, and I can count on one hand who kept clean diets. The big difference between the old timers and the new guys is the old timers stayed fit with lots of volume training whereas the newer guys will just shove anything into their gullet along with GH, slin IGF and whatever else -- ANYTHING to just get bigger.
I'd say 90% of the people using gear are only getting a fraction of the benifits because they don;t eat enough.
Don't get me started on "cutters" and "clean bulking."