I was vegan for almost an entire year back in '09 and it was the best I'd ever felt in my life. Boundless energy, happiness, inspiration. So many healthful benefits. Not to mention, with the inclusion of fasts, 30-40 lbs lost and kept off for a year.
Went on a hiatus, and gained a lot of weight back, not all of, but half of it. Along with losing all those things I talked about above (not completely).
I fast, but I like to do it the *healthy* ways, in this case-- with lots of water, raw veggies (mostly salads without dressing, or a little vinegar or lemon for dressing), some fruits (mostly high water content varieties), and fresh juices (mostly veggie) and smoothies (for example, berries, spinach and flax).