I don't have the correct answer for you.

I watched What's Eating You? a few nights ago and it was about two anorexics. One binged/purged all day long and she was anorexic. I was also under the impression that that was bulimia. But bulimics can maintain their weight to where people usually can't tell by looking at them that there's a problem.

This girl drank 30 bottles of diet soda in a couple of days and ate everything in sight... but threw it all up. She was SO thin.