Not the way I see it. I'm a brain cancer survivior that has done some fasting and running. I've fasted for 72 hours twice in the last year and a half. The fasting reasoning is based on evidence of studies out of the University of California. There's empirical evidence showing that severe caloric restriction "reboots" a person's immune system. My immune sytem let me down by allowing some out of control cells to grow in my head, so I've "rebooted" it twice. Maybe it'll help in the long run. In the short term, I've become much better acquainted with my actual caloric needs. Those needs are much less than I thought. Not only that, I ran two miles after fasting for nearly 70 hours. I was pretty fast and felt great. How many folks can lay claim to that? Potential of cancer regrowth aside, I can't really say I've felt a whole lot healthier ever before.