I had heard about people who have eating disorder tend to have other disorders as well, like obsessive compulsive disorder.  Things like only eating a certain number of food in a sitting.  Having to do squats a certain number of times in the shower while putting shampoo in their hair.  That is why it is so important that clinics and outpatient treatment for eating disorders to offer the therapy sessions.  Group and individual sessions are so important for the patients to really understand why they do what they do.  Where a need to obsess over this one thing in their life, and not something else.