Differences Between Bulimia Nervosa and Anorexia Nervosa Binge-Purge Subtype
The key distinction between bulimia nervosa and anorexia nervosa binge-eating/purging subtype is body weight status: individuals with anorexia nervosa maintain significantly low body weight, while those with bulimia nervosa typically have normal or near-normal body weight. 1, 2
Core Diagnostic Features
Bulimia Nervosa
- Characterized by recurrent episodes of binge eating followed by inappropriate compensatory behaviors to prevent weight gain 1
- Requires these behaviors to occur at least once a week for 3 months according to DSM-5 criteria 1
- Self-worth is overly based on body shape and weight 1
- Patients typically maintain normal or near-normal body weight 3
- Patients are often aware of their eating difficulties and experience marked distress 3
Anorexia Nervosa Binge-Eating/Purging Subtype
- Characterized by restriction of food intake leading to significantly low body weight, along with binge eating and/or purging behaviors 2
- Core features include intense fear of weight gain and body image distortion 2
- Significantly lower than expected body weight is maintained despite binge-purge behaviors 2
- Patients often deny their illness or its severity 3
Clinical Presentation and Behaviors
Shared Features
- Both conditions involve episodes of binge eating and compensatory behaviors such as self-induced vomiting, laxative abuse, periods of starvation, or excessive exercise 1, 2
- Both conditions are associated with body image disturbance as a core symptom 3
- Both can lead to serious medical complications, particularly related to purging behaviors 4
Distinguishing Features
- Purging behaviors in anorexia nervosa binge-purging subtype occur in the context of significantly low body weight 2
- In bulimia nervosa, purging is primarily aimed at preventing weight gain after binges, while maintaining normal weight 1
- Anorexia nervosa patients (including the binge-purge subtype) display medical complications related to malnutrition and underweight that are not typically seen in bulimia nervosa 4
Medical Complications
- Anorexia nervosa is associated with complications related to malnutrition and underweight, including hypothermia, bradycardia, and hypotension 2, 4
- Both conditions can present with hydro-electrolyte and acid-base disturbances due to purging behaviors 4
- Early identification and intervention are critical as mortality rates for eating disorders are among the highest for any psychiatric disorder 1, 2
Treatment Considerations
- For adults with bulimia nervosa, the recommended treatment is eating disorder-focused cognitive-behavioral therapy (CBT) along with a serotonin reuptake inhibitor (typically fluoxetine 60 mg daily) 1
- For adolescents with bulimia nervosa who have involved caregivers, eating disorder-focused family-based treatment is suggested 1
- Treatment for anorexia nervosa binge-purge subtype must address both the weight restoration goals and the binge-purge behaviors 2, 4
Clinical Implications
- Despite having different diagnostic criteria, research shows that individuals with anorexia nervosa binge-purge subtype display levels of psychopathology more similar to bulimia nervosa than to restricting-type anorexia nervosa 5
- Patients with anorexia nervosa binge-purge subtype may exhibit higher levels of core eating disorder psychopathology compared to restricting subtype, despite similar levels of eating disorder-related impairment 6
- Weight/shape concerns and binge eating frequency are significant predictors of functional impairment in both conditions 6
Common Pitfalls in Diagnosis
- Focusing solely on weight status without assessing for binge-purge behaviors may lead to missed diagnoses 1, 2
- The transition between diagnoses is common, with some patients moving from anorexia nervosa to bulimia nervosa as weight is restored 3
- Purging behaviors, regardless of whether objective binge episodes are reported, may be a more meaningful marker for subtyping anorexia nervosa than the presence of binge eating 5