I'm sure there are lots of health benefits to water fasting. But I think these are outweighed by the problems with it. Crash diets very rarely work, where weight is lost so fast and then put on even more afterwards. With water fasting people lose around 1kg (2 pounds) a day. What did you expect? You are not eating. It can not only be bad for your body's health and your minds health. But you will have bunch of flappy loose skin from losing weight so fast. That is probably the worst after effect of it, aside from all the misery from starving yourself. But hey, to each their own. Just my thoughts.