[Evgeny]

My advice for anyone interested in fasting would be to go slow. If never tried it before, start with a 24 hour fast - i.e. eat dinner, then nothing until dinner time the next day. If that went fine, next week try a 36 hour fast - i.e. dinner, no food the next day, and eat breakfast the day after. If that goes well again, continue extending the fasting time, but also allow yourself time in between. Eventually you will get a grasp and some feeling about how long is too long, or how often you can do fasts - I don't think there is much science on the topic.

I did 36 hour fasts, then I did 48 hour fasts, then I went for 3 days, then for 4, finally for 5 - over a course of several years actually. May try a longer fast in the future, but my current schedule is to have a weekly 36 hour fast - at least, most weeks.