Alternate Day Fasting Improves Physiological and Molecular Markers of Aging [pdf]
I fast, on average, once a week. At least once a month, I try to do an extended fast (2-5 days) to force ketosis. I also do intermittent fasting basically daily (I only eat between 12-8). Been doing this for about 4 years now. Some anecdata:- Fasting > 24 hrs paradoxically gives you an extreme boost of energy and mental focus. I especially love how my olfactory sense is extremely heightened. It's pretty cool and even after all these years doesn't get old.- Fasting is not a panacea. Depriving yourself of nutrients or eating garbage is still a bad idea even if you fast or do IF. Unfortunately, eating healthy is hard and kinda' sucks. Egg whites and chicken + broccoli gets old pretty fast.- Fasting >7 days is a bad idea unless you know what you're doing.  This is when your muscles and vital organs start contributing as an energy source (e.g. they also start breaking down).- Your body is clever, so extended fasts will start putting you into "starvation mode" and you'll lose some of the benefits.- There have been NO STUDIES on long-term fasting (e.g. over the course of an adult lifetime). This is a big warning sign to just be careful and not overdo it. Different people have different tolerances. Talk to your doctor.- Even on fast days, make sure you take vitamins (I take Fish Oil, Zinc, a Multivitamin and Magnesium)