"Eating disorder, not otherwise specified" is kind of this long, too many words term that's kind of a catch all phrase within the Diagnostic Manual most commonly used amongst mental health professionals in the United States, the DSM IV. It's kind of a catchall diagnosis to refer to a lot of different types of eating disorder problems that don't neatly follow into the other eating disorder diagnosis categories. So they don't neatly fall into the category of either anorexia nervosa, or bulimia nervosa.
So currently in the DSM IV, "Eating disorder, not otherwise specified" refers to a variety of different types of eating problems such as binge-eating disorder, such as night-eating syndrome, and such as purging disorder. And "Eating disorder, not otherwise specified" also refers to a variety of different types of restrictive tendencies, or binge eating or purging tendencies, that don't quite meet the criteria for anorexia nervosa or bulimia nervosa.
"Eating disorder, not otherwise specified", because it is such a broad category, currently represents the majority of eating disorder diagnoses. With the revision of the Diagnostic Manual, the DSM IV, conversion into DSM V, which has been happening over the past few years and will probably roll out in the coming year or so. We expect there to be somewhat fewer "Eating disorder, not otherwise specified" diagnoses, because new diagnostic categories are being added to the DSM, like "Binge-eating disorder". So that folks with binge-eating disorder are expected to now receive their own diagnosis of binge-eating disorder, and will no longer be called, "Eating disorder, not otherwise specified".
Still in the confirmation process, the book hasn't come out yet. So until it does, stay tuned, but that will be one step that will reduce the use of that type of diagnosis, and get at trying to be more specific about some of those types of eating problems in the future.