# Bulimia Nervosa and Binge Eating Disorder

## Introduction

**Bulimia nervosa (BN)** and **binge eating disorder (BED)** are eating disorders characterized by recurrent episodes of binge eating. BN involves compensatory behaviors to prevent weight gain, while BED does not. Both conditions cause significant psychological distress, medical morbidity, and functional impairment. Unlike anorexia nervosa, effective pharmacotherapies exist for both BN and BED, and cognitive behavioral therapy has a strong evidence base.

## Bulimia Nervosa

### DSM-5 Criteria

Recurrent episodes of **binge eating**: consuming an objectively large amount of food in a discrete period with a sense of loss of control. Recurrent inappropriate **compensatory behaviors**: self-induced vomiting, laxative or diuretic misuse, fasting, excessive exercise. Binge eating and compensatory behaviors occur at least **once per week for 3 months**. Self-evaluation is unduly influenced by body shape and weight. Disturbance does not occur exclusively during episodes of anorexia nervosa.

### Epidemiology

Lifetime prevalence: approximately **1-1.5%** in women, 0.5% in men. Typical onset: late adolescence to early adulthood. Patients are often at **normal or slightly above normal weight**, making the disorder less externally visible.

### Medical Complications

**Electrolyte abnormalities**: hypokalemia and metabolic alkalosis from purging (the most dangerous acute complications) **Dental erosion** (perimolysis): loss of enamel on the lingual surface of teeth from gastric acid exposure. **Parotid gland hypertrophy** (chipmunk facies) **Russell's sign**: calluses on the dorsum of the hand from induced vomiting. Esophageal tears (Mallory-Weiss), rarely esophageal rupture (Boerhaave syndrome) Cardiac arrhythmias from electrolyte disturbances. Metabolic acidosis from laxative abuse. Ipecac cardiomyopathy (from ipecac misuse; now rare)

![Medical complications of bulimia nervosa organized by organ system](images/bulimia-medical-complications.png)

### Treatment of Bulimia Nervosa

#### Psychotherapy

**CBT-E (Enhanced)** is the first-line treatment; typical course is 20 sessions over 20 weeks. Addresses dietary restraint, overvaluation of shape and weight, and interpersonal triggers. Approximately 50% of patients achieve binge-purge abstinence with CBT. **Interpersonal psychotherapy (IPT)** is an effective alternative, though slower in onset. **Guided self-help based on CBT** is effective for less severe cases.

#### Pharmacotherapy

**Fluoxetine 60 mg/day** is the only FDA-approved medication for BN; produces a 50-70% reduction in binge-purge frequency. The effective dose is higher than the typical antidepressant dose. Combination of CBT + fluoxetine may be superior to either alone. Other SSRIs and topiramate have evidence but are not FDA-approved for this indication. **Bupropion is contraindicated** in BN due to increased seizure risk with purging-related electrolyte imbalances.

## Binge Eating Disorder

### DSM-5 Criteria

Recurrent episodes of binge eating (as defined above) Episodes are associated with three or more of: eating rapidly, eating until uncomfortably full, eating large amounts when not hungry, eating alone due to embarrassment, feeling disgusted, depressed, or guilty afterward. Marked distress regarding binge eating. Occurs at least **once per week for 3 months**. **Not associated with compensatory behaviors** (distinguishes BED from BN)

### Epidemiology

Lifetime prevalence: approximately **2-3%**, the most common eating disorder. More evenly distributed across genders than AN or BN (approximately 3:2 female-to-male ratio) Strong association with **obesity**: present in 25-50% of individuals seeking bariatric surgery. Higher prevalence in racial and ethnic minority groups compared to AN and BN.

### Associated Features

Frequently comorbid with depression, anxiety, ADHD, and substance use disorders. Associated with metabolic syndrome, type 2 diabetes, and cardiovascular disease. Emotional and stress-related eating patterns are prominent. Shame and secrecy often delay presentation for treatment.

### Treatment of Binge Eating Disorder

#### Psychotherapy

**CBT** (individual or group) is first-line; reduces binge frequency by 50-80%. CBT does not typically produce significant weight loss; this may require additional interventions. **IPT** is also effective. **Dialectical behavior therapy (DBT)** adapted for BED addresses emotion regulation deficits. **Behavioral weight loss (BWL)** programs may reduce bingeing and produce weight loss simultaneously.

#### Pharmacotherapy

**Lisdexamfetamine (Vyvanse)**: the only FDA-approved medication for moderate to severe BED; reduces binge frequency; doses of 50-70 mg/day. SSRIs (sertraline, fluoxetine) reduce binge frequency but have modest effect sizes. **Topiramate**: reduces binge frequency and promotes weight loss; limited by cognitive side effects. **GLP-1 receptor agonists** (semaglutide, liraglutide): promising for BED with comorbid obesity; emerging evidence. Avoid prescribing appetite suppressants without addressing the underlying eating disorder.

![Comparison of treatment approaches for bulimia nervosa and binge eating disorder](images/bn-bed-treatment-comparison.png)

## Distinguishing BN from BED

| Feature | Bulimia Nervosa | Binge Eating Disorder |
|---|---|---|
| Binge eating | Present | Present |
| Compensatory behaviors | Present (required) | Absent |
| Body weight | Usually normal | Often overweight or obese |
| Self-evaluation based on shape/weight | Core feature | Variable |
| FDA-approved medications | Fluoxetine | Lisdexamfetamine |

## Assessment Approach

### Clinical Interview

Ask about binge eating with specific quantities and duration to confirm objectivity of binges. Screen for all compensatory behaviors, including less recognized ones (diet pill misuse, insulin restriction in type 1 diabetes) Assess for comorbid mood, anxiety, and substance use disorders. Obtain a dietary history and eating patterns.

### Medical Evaluation

Electrolytes (especially potassium, bicarbonate, chloride) Serum amylase (elevated salivary fraction suggests purging) ECG if electrolyte abnormalities or cardiac symptoms are present. Dental examination referral for purging patients.

### Screening Tools

**Eating Disorder Examination Questionnaire (EDE-Q)**. **SCOFF Questionnaire** (5-item screening tool) **Binge Eating Scale (BES)** for BED.

![Clinical assessment flowchart for suspected binge eating and purging disorders](images/binge-eating-assessment-flowchart.png)

## Key Clinical Pearls

Bulimia nervosa is often invisible; patients are typically normal weight and may not disclose purging without direct inquiry. Hypokalemia is the most dangerous acute medical complication of BN; obtain electrolytes in all suspected cases. Bupropion is absolutely contraindicated in bulimia nervosa. BED is the most common eating disorder and is underdiagnosed, particularly in primary care settings. Weight loss should not be the primary goal of BED treatment; reducing binge eating and psychological distress takes priority.

## References

1. Shapiro JR, Berkman ND, Brownley KA, et al. Bulimia nervosa treatment: a systematic review of randomized controlled trials. *Int J Eat Disord*. 2007;40(4):321-336.
2. McElroy SL, Hudson JI, Mitchell JE, et al. Efficacy and safety of lisdexamfetamine for treatment of adults with moderate to severe binge-eating disorder: a randomized clinical trial. *JAMA Psychiatry*. 2015;72(3):235-246.
3. Fairburn CG, Cooper Z, Doll HA, et al. Transdiagnostic cognitive-behavioral therapy for patients with eating disorders: a two-site trial with 60-week follow-up. *Am J Psychiatry*. 2009;166(3):311-319.
4. Wonderlich SA, Gordon KH, Mitchell JE, et al. The validity and clinical utility of binge eating disorder. *Int J Eat Disord*. 2009;42(8):687-705.