You're right, technically it does.  Of course, any fat girl who is told she has atypical anorexia (where the weight requirement is not met) is still going to tell everyone how much she's suffered because of her "anorexia."  I'm also convinced that, similar to things like hypothyroidism, a lot of fat girls will see someone else using the condition as an excuse and self-diagnose. I'd like to believe that doctors don't diagnose overweight people with anorexia, but I was hospitalized for anorexia years ago and there was a fat woman on our unit that was there for anorexia.  She had lost over half her body weight in a short period of time after a family tragedy.  The rest of us didn't really understand why she was there, considering she didn't look like she was going to starve to death any time soon.