"advice: don't do it.
The only benefits from fasting (in my opinion) would be mental/spiritual, but from a strictly physical stand point...fasting is neutral at best. The body doesn't require any detoxing, that's what your liver/kidneys/GI tract are for. Whatever weight you lose would be water weight, which you would quickly regain once you resume eating. Why put yourself through starved, weakened, misery to just drop a few lbs of water weight?
You would do yourself a huge favor to just resume eating in a healthy manner, and engage in regular physical activity."