About a year ago, I did two extended water fasts (24 and 16 days, about 8 weeks apart). I wanted to do a single 40 day one (just for kicks, to see if I last) but stopped after 24 days as I wasn't feeling well.

I've lost 18 kg during the first one (102 kg -> 84 kg), then quickly regained about 4 kg, and lost about 10 kg during the second one (88 -> 78). After the second fast, I started resistance training between two and four times a week (with a brain-endowed gym coach). I'm currently down 14 kg (88 kg), but gained quite a lot of muscle.

Though I can't recommend water fasting on blanket terms, if you're like me and you prefer short-term intense stress to long-term baseline stress, you may find that it's a great way to lose a lot of weight quickly, start feeling better about yourself and what your body is capable of, and get on the path to a healthier life style.

It was truly a remarkable experience.

For me, the trigger was https://www.youtube.com/watch?v=yaWVflQolmM.