For some people weight control means going to extreme measures to lose a few pounds. Unless those measures are kick up the work outs and/or eliminating junk food, I am not an advocate of traumatizing your body.
Unless you are doing a cleanse for religious or medical purposes, I can not understand why anyone would put themselves in potentially dangerous situation by fasting. Fasting to lose weight just isn't smart. Anorexia, bulimia and bingeing can have serious irreversible side effects.
Here are a few taken from Health magazine :infertility, heart problems, tooth decay, bloating and overdosing on self medications.
I am surprised that people would rather hurt themselves than help themselves by (lets say) running a few miles.