The only IFBB Pro who I have trained with would rely mostly on food. He did not have a big name supplement sponsor but it seemed like he would only use an occasional pre-workout stimulant drink or sometimes post-workout shake, not a whole lot else.
On the other hand when you look at amateur and natural bodybuilders a lot of them rely heavily on supplements. At the Pro level how your body responds to drugs, genetics, and how far you want to push it are the seperating factors.
Protein, Creatine, and Fish Oil would be beneficial supplements for anyone. A lot of the other products on the market such as NO-Products, Glutamine, PH's, etc. are just money makers for supplement companies.
