It's not so much that I don't exercise, although I presumed that my right to party wasn't quite what the question had in mind.
Basically, The way I see it, is mind over matter. I've willed my metabolism into high gear by refusing to acknowledge that so called bad junk foods do anything but help me.
Although the fact that my diet and activities haven't really changed much in years probably helps; my body is down right used to my sedentary gamer lifestyle, and knows exactly how to handle what I throw at it.