I recently did my first 3 day water fast. No food, just spring water for 3 days and 3 nights. I did it after being inspired by the BBC's Horizon program
Eat, Fast and Live Longer. It's well worth an hour of your time.
Now that i've kickstarted this with the 3 days I am doing daily 16hr fasts. Dinner at 17:30, then nothing till breakfast at 09:30 and 1 day a week I am doing a 24hr fast. (eat dinner, then not again till dinner next day). And that's today!
It's early days yet but I can say that the effects of the 3 days were astonishing. 3 days is considered quite a short fast by the standards of the folks at
FastingConnection but I feel lighter (in being, spring in step kind of way), way sharper in mind and have tons more energy! Oh, and going with that energy has come motivation, clarity and some intuitive forward thinking. Also, many of my aches and pains disappeared during the fast, though they have come back a bit since breaking it (something to work on..)
Of course it helps that Im currently enjoying a fairly solid baseline of Equanimity

I can now understand why when I come back off retreat I feel many of the same things. The typical Theravadin schedule is a daily 20hr fast (ish). Typically after about day 3 or 4 all my aches and pains start disappearing and I've usually tightened my belt by the time I get back.
The health benefits of daily / weekly short "maintenance fasts" are fairly well documented in the BBC program. It really seems like the Intermittent approach could be a middle way to better health congruent with buddhist teachings and practice.
For more, see
AllAboutFasting.com which is probably the best resource I've found so far in my research. Also, this
series on the benefits of intermittent fasting by "primal blueprint" author Mark Sisson.
If you've done this kind of thing before, let us know what you think..