The DSM-5 remains the best approach to categorizes mental disorders, even though it has serious limitations, like no real psychobiological underpinning for any its conditions and arbitrary lines between normal and abnormal. The research is hampered by incoherence, as the definition ( i.e. the inclusion criteria) of who is considered a subject is quite inconsistent between groups. Nevertheless, the DSM-5 has obviously put in a huge amount of time and energy, focus group work, field trials, and expert opinion in generating the Feeding and Eating Disorder section of their work.
Off the bat, I want to introduce something new Remarkably, there has been the addition of a previously unknown disorder: ARFID, or Avoidant/Restrictive Food Intake Disorder. It explains itself. Individuals who are very picky about what they eat to such an extent that it ruins their lives– to make a hyperbole of it. Basically, the disorder seems to emerge in adolescence, and involves restriction, not for the purpose of weight loss i.e. anorexia nervosa, but more because eating is aversive and unpleasant; it leads to nutritional deficiencies, social fallout, significant weight loss, and dependence on nutritional supplements. It is a lower order diagnosis which would be subsumed under the umbrella of anorexia or bulimia if the preoccupation with body weight and appearance were also present. In sum, it’s a new diagnosis and not necessarily studied enough to establish a set prevalence, but estimated to be less than 1% of the population.
The other major DSM-5 change was the full-fledged acceptance of BED, Binge-Eating Disorder, which is basically bulimia without the purging, and not to be confused with gluttony. Weight and body image do not enter into the diagnosis. It is about binge eating. It has to be distressing to the individual, and is characterized by extreme food intake in a short period of time. They forgot the numbers? Well, the DSM-5 dropped numbers in favor of a more clinical approach left to the expertise of the diagnostician. [Why?! It only leads to the problems of incoherence again, and force us to use other guidelines.] So, roughly, I gather, most experts would say that a binge is more than 1000 calories consumed quickly with an intense loss of control, done at least once a week for 3 months minimum, and causes distress and discomfort. Apparently, when applied strictly by these full DSM-5 criteria, BED only captures 1% of the population. (um, that’s millions of Americans, and 100,000’s Canadians….) .
Anorexia and Bulimia Nervosas also afflict 1% of the population, and supersede all lower order diagnoses in the hierarchy: Anorexia nervosa is at the top of the hierarchy, and is uniquely characterized by extreme thinness, and involves either restricting food to prevent weight gain or excessive binging and purging to avoid weight gain; bulimia just involves binging, and then compensatory purging to prevent weight gain, but does not involve extreme thinness. Both Anorexia and Bulimia involve self-evaluations “unduly influence” by body image and are thus different from ARFID or BED. ARFID behaviors can occur in AN or BN, and would then not be a seperate disorder, unless you really wanted to highlight. BED is part of BN when there is compensatory purging.
Note: compensatory behaviors for binges involve more than self-induced vomiting, for it can also involve laxative abuse, misuse of diuretics, excessive weight loss medications, fasting, or excessive exercise. Note #2: It hits men, too.