Don't eat. Seriously. Try fasting. It's quite fun, in a frustrating sort of way. The longest I've gone is four days. Then I broke down and stuffed myself with Taco Bell.

Or, work out when you're baked. I like to. It's pretty easy to get a Zen thing going. But if you want to get the Zen, it's important not to have distractions. No music, no nothing. Just sit in your room and do shitloads of sit-ups and push-ups. But remember, if you want to lose the gut, sit-ups won't do it alone. Leg lifts are much better.

And yeah, like the Monkey said, drink lots of water. It's fun. You get to pee a lot.