I fasted for two weeks and three days. That's 17 days. Without eating anything, nor drinking anything other than water. Yes, I finally passed out, and it was at school... And I wasn't really exercising, it was because I was walking down the hall (high school) and I became extremely dizzy and passed out. I would have completely fallen on the hard floor, but a random guy was walking behind me, and he caught me...
In those two weeks I lost 11 lbs. When I started, I was 101 lbs, and now I am 90 lbs. I am also 5'11'', in case you were wondering. I don't think you'll pass out if you just fast for a few days.... I don't know.... Just don't fast.
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