I’ll spare you the physiological details of my three-day water fast, other than to say that it was generally unpleasant, that I reached a point of extreme hunger that subsided by the third day, and that 24 hours after I started back on solid food I felt purified and ecstatic, about as good as I have in my entire adult life.

The fast seemed to have a rebooting effect. My cravings for beer and ice cream (two pillars of my personal diet) all but vanished. I could normally force myself through a few three-mile jogs every week, but now my endurance skyrocketed, even as I consumed about half my usual calories. I ran a half-marathon with ease just a month later.

Subsequent fasts conjured similar results and went even more smoothly after a trainer friend suggested I sneak some salt into my beverage. (My physician was delighted with my fitness but horrified by my methods: "This can’t be good for your kidneys," he told me.) I’ve never been a particularly flexible person, but during a later fast I found that I could touch my toes for the first time in years, and then place my palms on the floor. A chronic respiratory ailment vanished, and a year later it has yet to return. I still can’t explain it.

Next: Experiment No. 2: Extreme Walking