I'd have to stand by you on this one man. ($ick3nin.v3nd3tta)
Short term the body can withstand just about any source of fuel, but long term you're really going to be impairing a lot of systems by not eating properly. And we all know that real progress is made over long periods of time.
It's not rocket science however. Protein. Carbohydrates. Fats. + Vitamins and Minerals. All have their purposes: protein for a more athletic physique, carbohydrates for...energy duh. And fats, (not all of 'em) actually have good cardiovascular properties. Just eat plenty of water and try to base your diet on everything whole. Not always possible, and it's alright, but if you're going to buy your own stuff at a grocery store, make sure to buy quality stuff. And it's not like it'll cost you a lot more.
Personally, I feel like nutrition is slowly being snubbed, when it's in fact the key for consistency. IMO.
oh and just like that, nothing wrong with mcdonalds (or fastfood) to me, especially not the burgers on the value menu.