Can you have bulimia nervosa (BN) if you are underweight?

Yes, You Can Have Bulimia Nervosa While Being Underweight

According to the Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition (DSM-5) criteria, it is possible to have bulimia nervosa while being underweight, as the previous weight threshold requirement has been eliminated from the diagnostic criteria. 1

Understanding Bulimia Nervosa Diagnosis

• Bulimia nervosa (BN) is characterized by recurrent episodes of binge eating followed by inappropriate compensatory behaviors to prevent weight gain, such as self-induced vomiting, laxative abuse, periods of starvation, or excessive exercise 1, 2
• The DSM-5 diagnostic criteria for BN require these behaviors to occur at least once a week for 3 months, with self-worth being overly based on body shape and weight 1
• Importantly, the DSM-5 criteria for BN are less stringent than previous versions, which has increased the number of reported cases 1

Distinguishing Between Eating Disorders in Underweight Individuals

• The key distinction between anorexia nervosa binge-eating/purging subtype and bulimia nervosa is primarily based on weight status 3, 4
• If an individual is significantly underweight and engages in binge eating and purging behaviors, they would typically be diagnosed with anorexia nervosa binge-eating/purging subtype rather than bulimia nervosa 3, 4
• Research has found that underweight individuals can experience both objective bulimic episodes (consuming objectively large amounts of food with loss of control) and subjective bulimic episodes (perceived overeating with loss of control) 4

Clinical Implications and Assessment

• The American Psychiatric Association recommends comprehensive assessment of patients with possible eating disorders, including vital signs, height, weight, BMI, and physical appearance for signs of malnutrition or purging behaviors 1
• Laboratory assessment should include a complete blood count and comprehensive metabolic panel, with particular attention to electrolytes, liver enzymes, and renal function tests 1
• An electrocardiogram is recommended for patients with restrictive eating disorders or severe purging behaviors due to potential cardiac complications 1, 5

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, 2
• For adolescents and emerging adults with bulimia nervosa who have involved caregivers, eating disorder-focused family-based treatment is suggested 1
• Treatment should address both the psychological aspects (fear of weight gain, body image disturbance) and the behavioral components (normalizing eating patterns, eliminating compensatory behaviors) 1, 2
• Medical monitoring is crucial regardless of weight status, as purging behaviors can lead to serious electrolyte imbalances and acid-base disturbances 5, 6

Medical Complications

• Bulimia nervosa can cause serious medical complications affecting multiple body systems, particularly renal and electrolyte systems, regardless of the patient's weight 5, 6
• Purging behaviors (self-induced vomiting, laxative abuse, diuretic abuse) can lead to dehydration, electrolyte abnormalities, and acid-base disturbances 5, 6
• Some medical complications may be reversible with behavior cessation, but others may persist 6

Important Clinical Considerations

• Early identification and intervention are critical as mortality rates for eating disorders are among the highest for any psychiatric disorder 3
• A multidisciplinary approach involving physicians, psychologists, and nutritionists is recommended for comprehensive care 5
• The similar treatment outcomes observed in underweight patients with different patterns of bulimic episodes suggest that the type or frequency of bulimic episodes may be of limited clinical utility in determining treatment approach 4