Bulimia Nervosa
Recurrent episodes of binge eating paired with recurrent inappropriate compensatory behaviors to prevent weight gain, occurring at least weekly for three months, with self-evaluation unduly influenced by body shape and weight.
Bulimia Nervosa vs. Anorexia Nervosa
Bulimia Nervosa is defined by recurrent binge-eating episodes with loss of control, paired with recurrent inappropriate compensatory behaviors (self-induced vomiting, laxative/diuretic misuse, fasting, excessive exercise) at least weekly for 3 months, with self-evaluation unduly influenced by body shape/weight -- occurring at a body weight that is NOT significantly low. Anorexia Nervosa requires restriction of energy intake leading to significantly low body weight, intense fear of weight gain, and body-image/shape disturbance.
Onset / developmental pattern
Both typically have onset in adolescence or young adulthood, often following dieting behavior. The trajectories can diverge from there: Bulimia Nervosa's binge-purge cycle can develop without ever crossing into significantly low body weight, while Anorexia Nervosa's restriction pattern progressively drives body weight down.
Duration / course
Bulimia Nervosa requires the binge-and-compensate cycle at least weekly for 3 months. Anorexia Nervosa's diagnosis rests on the presence of significantly low body weight plus the fear/behavior and body-perception criteria, without a fixed frequency threshold for any specific behavior.
Associated features
Bulimia Nervosa is associated with medical complications of purging specifically -- electrolyte disturbances, dental erosion, esophageal irritation -- often at a body weight in the normal-to-elevated range. Anorexia Nervosa is associated with the broader medical consequences of starvation itself -- amenorrhea-related changes, bradycardia, bone density loss -- stemming from significantly low body weight.
Functional impairment
Bulimia Nervosa's impairment centers on the binge-purge cycle's psychological and medical toll, occurring without the additional burden of significantly low body weight. Anorexia Nervosa's impairment includes both the psychological rigidity around food/weight and the serious, sometimes life-threatening medical consequences of significantly low body weight.
Rule-outs / exclusions
The defining exclusion between them is body weight: Bulimia Nervosa is specifically diagnosed when binge-purge behavior occurs WITHOUT meeting Anorexia Nervosa's significantly-low-weight criterion. If significantly low body weight is present alongside binge-purge behavior, Anorexia Nervosa, binge-eating/purging type, is the more accurate diagnosis rather than Bulimia Nervosa.
The differential question
Both can involve binge-eating and compensatory/purging behavior, which is why body weight is the decisive differentiator: significantly low body weight with these behaviors is Anorexia Nervosa (binge-eating/purging type); binge-purge behavior at a body weight that is not significantly low is Bulimia Nervosa.
Common student confusion
Because both disorders can include purging behavior, students sometimes try to distinguish them by the specific compensatory method used (vomiting versus laxatives, for instance). The actual deciding criterion is body weight, not the specific method of compensation.
Case clues
A 20-year-old at a body weight in the normal range binges several times weekly and self-induces vomiting afterward, with self-worth heavily tied to body shape -- Bulimia Nervosa. A 20-year-old at a significantly low body weight for her height engages in the same binge-purge pattern, with intense fear of weight gain -- Anorexia Nervosa, binge-eating/purging type.
Distinguishing table
| Feature | Bulimia Nervosa | Anorexia Nervosa |
|---|---|---|
| Body weight | Not significantly low | Significantly low body weight is a core diagnostic criterion |
| Behavior pattern | Recurrent binge-purge cycle, at least weekly for 3 months | Restriction, with or without a binge-eating/purging subtype |
| Diagnostic priority when weight is low | Not diagnosed if significantly low weight is present with these behaviors | Takes priority (binge-eating/purging type) when significantly low weight is present |
Clarifying questions to ask
Read each disorder in full
Anorexia Nervosa
Persistent restriction of energy intake leading to significantly low body weight, intense fear of weight gain or persistent behavior interfering with weight gain, and disturbance in self-perceived weight/shape.