There's an interesting article in the new Harper's about the potential health benefits of fasting ("Starving Your Way to Vigor" by Steve Hendricks). It cites a number of historical cases to refute the common wisdom that a person will die of starvation after 10 to 14 days. There are reported cases of people living much, much longer than that without food, assuming they are adequately hydrated, and especially if they are overweight to begin with. One grossly obese Scotsman supposedly went a full year without food, feeding solely off 276 pounds of excess body weight.
Hendricks names numerous studies in which short fasts reduce or eliminate the symptoms of various illnesses and diseases, some associated with obesity and some not. In one, a group of 174 hypertensives fasted for 10 days, and all but 20 of them had normal blood pressure by the end of the fast; the average drop was greater than has been reported in any drug study, and six months later most were still maintaining a healthy blood pressure. In another, cancer patients who fasted prior to and during chemotherapy suffered fewer side effects. Rats who fasted every other day prolonged their life spans. There's a treatment for epilepsy that involves fasting for several days, followed by adherence to a strict high-fat, low-carbohydrate diet; discovered decades ago, it has recently come back into favor and is known to be far more effective in preventing seizures than drug therapy in some patients. The author himself fasts for 20 days (with daily exercise) and loses 20 pounds.
Given my interest in outsider health stories and self-experimentation, I of course find all this fascinating, but I do think it's strange that the author doesn't address calorie restriction, known to prolong lifespan in pretty much every species for which it's been tested, as a method distinct from fasting; long-term calorie restriction doesn't require fasting per se, and humans who voluntarily adopt calorie-restricted diets have reported similar health gains (and weight loss, natch).
I kind of want to do a brief fast, not to lose weight but to give my intestines a chance to heal up completely. They seem to be in a constant state of slight disrepair, though certainly much better than they were when I was eating gluten all the time. My guess is that not eating anything for a few days would do my gut good. I'm too paranoid to try in earnest, though, because I have a history of fainting when my blood sugar gets low; one of these episodes sent me to the ER in need of stitches (in my face, no less). So it seems unlikely that I'll get a chance to try it out, unless some nearby hospital runs a study and I can volunteer as a subject, hence doing it under medical supervision. That would be swell, especially if they paid me. How about it, science?