Let's just say that somehow--magically, okay--junk food and all its nasty varieties became healthy. Better yet, let's say that you could eat whatever you wanted and as much as you wanted, and it would have no negative effect whatsoever.
Personally, since I haven't had them in ages, my initial reaction would be to buy a few dozen of those doughnuts with the cream feeling and eat and eat and eat.

And then I would drink milkshakes every day and sleep on a bed of hot fudge. Mmmmmm *drool* hot fudge