I have fasted off and on for about 3 or 4 years now without any affects. I am much more healthier then I was before that time.
3 years ago I water fasted for 55 days, with NO ILL AFFECTS at all. I felt more alive, revived, refreshed and renewed more then anything.
There are cautions that a person should be take, because health problems can spout up during a fast, which need to be taken care of if they show themselves, but fasting itself is not as dangerous to do. It has been being done for centuries.