Most of the time the difference between steady gaining or losing weight is a few hundred calories a day. That's far from a lifestyle change.
When moving around becomes difficult, when dating becomes harder, when the aches and pain start... there's gotta be more to it than just a lot of sugar in your everyday stuff.
I always wonder (for other drugs too), if they're a way to slowly remove yourself from situations, or whatever it is, that make you uncomfortable. A way to permanently disqualify yourself from the race, because the idea of running (no pun intended) makes you anxious?