Don't talk like you know anything about biology, bitch.
You can weight 500 pounds on a 5'5 frame and stop eating for a month and still be 480 pounds. When you starve yourself through anorexia, your body goes into starvation mode and starts conserving energy in any way it can, greatly diminishing your usual metabolism.
You can be anorexic and still be obese because of this. When you go so far as to starve yourself, even only eating enough to stay alive, your body will do its best to stretch those tiny calories into what you used to feed it when you stuffed your face constantly.