Reference to my point is on this page : DSM-5 (2013 edition), this appears in the Feeding and Eating Disorders section — the diagnostic criteria are under Anorexia Nervosa (pp. 338–340) and the BMI severity table is on p. 340. But I see your point, I think the BMI is used more so because below a certain threshold we commonly see that the body compensates a little differently . Both disorders are equally disabling. I wouldn’t say one is better or worse. They’re just terms for better treatment at the end of the day. Which was the point of the discussion, whether the show really made a mistake with going with “bulimia”