I think fasting for 2 days is a bit extreme and possibly unnecessary. From my experience, it's the regular period I go through where I fight the urge to eat when hungry - the panic phase sets-in, but not long after it subsides. Coming out from that is elevating, character building, and it cleanses your mind because it focuses on one thing only when hungry, which you ignore and come out on top, stronger, more alert; positive.
Or, you can buy an expensive shake to do the task for you, which is, in effect, eating nothing but thinking you have. Nothing is achieved: the shake does not make you lose weight, it's the displacement of eating anything else that's the key. Do the same, but without the shake - it won't kill you.
