With or without steroids you'll need to add more and more to increase the gains, In this case food. The thing when your new to working out is that you almost automatically have a body working in the same way as with steroids, especially at young age.
The body transforms extremly fast if you just work out hard even without eating an extremly clean diet. After being the biggest guy at the gym or just a muscular guy the gains really starts to slow down heavily and that's when you see the difference with people taking this seriously.
Now food really starts to matter, living an healthy lifestyle and working harder than the others. I think the hardest thing to do natural is to become huge and lean, staying at 130-180 range I see as a much more resonable way to be in an outstanding shape natural.