Key Differences Between Anorexia Nervosa and Bulimia Nervosa
The fundamental difference between anorexia nervosa and bulimia nervosa is body weight: individuals with anorexia nervosa maintain a significantly low body weight through food restriction, while those with bulimia nervosa typically have normal or near-normal body weight despite engaging in binge-eating followed by compensatory purging behaviors. 1, 2
Core Distinguishing Features
Body Weight Status
- Anorexia nervosa is defined by significantly lower than expected body weight resulting from severe food restriction 1
- Bulimia nervosa patients maintain normal or near-normal body weight despite their eating disorder behaviors 2, 3
- This weight distinction is the primary diagnostic criterion that separates these two conditions, even when purging behaviors are present in both 2
Eating Behavior Patterns
- Anorexia nervosa is characterized by persistent restriction of food intake, often manifested as self-induced starvation 1, 4
- Bulimia nervosa involves recurrent episodes of binge eating (consuming large amounts of food with a sense of lack of control) followed by inappropriate compensatory behaviors 1, 2
- The compensatory behaviors in bulimia include self-induced vomiting, laxative abuse, fasting, or excessive exercise, occurring at least once weekly for 3 months 1, 2
Psychological Presentation
- Patients with anorexia nervosa typically deny their illness and may not recognize the severity of their condition 3
- Patients with bulimia nervosa are often acutely aware of their eating difficulties and frequently present as miserable about their condition 3
- Both disorders share intense fear of weight gain and disturbance in how body weight or shape is experienced 1
Epidemiological Differences
Age of Onset
Prevalence
- Lifetime prevalence in adolescent females: anorexia nervosa 0.3%, bulimia nervosa 0.9% 1
- Both conditions affect predominantly females with a female-to-male ratio of approximately 9:1 1
Important Clinical Distinction: Anorexia Nervosa Binge-Eating/Purging Subtype
A critical pitfall is confusing anorexia nervosa binge-eating/purging subtype with bulimia nervosa, as both involve purging behaviors. The key distinction remains body weight: anorexia nervosa binge-eating/purging subtype patients maintain significantly low body weight despite engaging in binge-eating and purging, while bulimia nervosa patients do not 2, 5
Medical Complications and Prognosis
Severity of Medical Complications
- Anorexia nervosa carries extremely serious medical risks including hypothermia, bradycardia, hypotension, and has mortality rates among the highest for any psychiatric disorder (4-11% mortality rate, with risk of death 12 times higher than age-matched general population) 5, 6
- Bulimia nervosa also causes significant medical complications through purging behaviors, particularly electrolyte disturbances and cardiac complications 2, 6
Treatment Outcomes
- The outcome of treatment for bulimia nervosa is reportedly better than that of anorexia nervosa 3
- For bulimia nervosa in adults: eating disorder-focused cognitive-behavioral therapy (CBT) combined with fluoxetine 60 mg daily is recommended 2
- For adolescents with bulimia nervosa: eating disorder-focused family-based treatment is suggested when caregivers are involved 2
Clinical Assessment Priorities
When evaluating patients, comprehensive assessment should include 2:
- Vital signs with particular attention to bradycardia and hypotension
- Height, weight, and BMI calculation
- Physical examination for signs of malnutrition (in anorexia) or purging behaviors (in both conditions)
- Laboratory assessment: complete blood count, comprehensive metabolic panel with focus on electrolytes, liver enzymes, and renal function
- Electrocardiogram for patients with restrictive eating or severe purging behaviors
Early identification and intervention are critical as eating disorders have among the highest mortality rates of any psychiatric disorder 2, 5