text: how fast can you lose weight if your bulimic?   it all depends on how much you puke or just don't eat and exercise. one time i ate only breakfast puked everything else up if i ate and i exercised a lot. by doing that i lost 15 pounds in three weeks. i'm sure if i watched what i ate at breakfast time i would have lost more. so it all depends on how much you are willing to put into it.