Bulimia Nervosa
High-Yield Comparison Between Eating Disorders
| Feature | Anorexia nervosa | Bulimia nervosa | Binge-eating disorder |
|---|---|---|---|
| Body weight | Significantly low body weight | Usually normal | No diagnostic weight requirement |
| Restricted intake | Core feature | May occur between binges as compensation | Not a core requirement |
| Binge eating | May occur in binge-eating/purging subtype | Required | Required |
| Compensatory behaviours (e.g. self-induced vomiting, excessive exercise) | May occur | Required | Absent |
| Weight gain / body-image concerns | Core feature (fear of weight gain + body image / weight disturbance) | Core feature (body image / weight disturbance) (fear of weight gain is NOT a core feature) | Not required |
| One-liner exam discriminator | Significantly low body weight + energy restriction (e.g. fasting) + fear of weight gain / body-image disturbance +/- binge eating or purging | Relatively normal body weight + binge eating + compensatory behaviours (e.g. excessive exercise, purging) + body-image disturbance | Recurrent binge eating without compensatory behaviours |
Causes and Risk Factors
The exact underlying cause of eating disorders is NOT fully understood.
Risk factors include: [Ref]
- +ve Family history (40-60% cases are heritable)
- Higher body weight
- History of overeating / binge eating / dieting / weight suppression / prior use of compensatory weight control behaviours
- Social and environmental pressures (pressure to be thin from parents, peers, and romantic partners)
- Body image concerns, including
- Deep internalisation and pursuit of the “thin ideal”
- Overvaluation of weight or body shape
- Fear of weight gain
- Feeling “fat”
- High levels of body dissatisfaction
- Psychological distress
Clinical Features and Diagnosis
DSM-5 Criteria
DSM-5 criteria for bulimia nervosa (ALL must be met): [Ref]
- Recurrent binge eating episodes, characterised by both
- Eating an excessively large amount of food within any 2-hour period (specifically defined as an amount of food that is definitively larger than what most individuals would eat in a similar period of time under similar circumstances)
- Feeling of not being able to stop eating, or control what or how much is eaten
- Recurrent inappropriate compensatory behaviours to prevent weight gain
- Non-purging behaviours: fasting, excessive exercise
- Purging behaviours: self-induced vomiting, laxative misuse, diuretic misuse, enema misuse
- The binge eating and compensatory behaviours occur at least once a week for 3 months (on average)
- Self-evaluation is unjustifiably influenced by body shape and weight
- The disturbances do NOT occur exclusively during episodes of anorexia nervosa
Classic binge eating-associated features (but not specified in the DSM-5 criteria):
- Eating unusually rapidly
- Eating until uncomfortably full
- Eating when not physically hungry
- Eating alone due to embarrassment
- Guilt / disgust / depression afterwards
Severity of bulimia nervosa is determined by the frequency of compensatory behaviours
- Mild: 1-3 episodes per week
- Moderate: 4-7 episodes per week
- Severe: 8-13 episodes per week
- Extreme: ≥14 episodes per week
Other Clinical Features
The following features can be seen in bulimia nervosa, but are not part of the DSM-5 criteria: [Ref1][Ref2]
| Category | Features |
|---|---|
| Physical signs |
|
| Features from purging behaviour |
|
| Psychiatric comorbidities | Mental health comorbidities are highly prevalent, including:
|
Complications
Key acute complications arise as a consequence of purging: [Ref]
- Dehydration → hypovolaemia and AKI
- Electrolyte disturbances (importantly hypokalaemia)
- QTc prolongation and arrhythmias (mainly secondary to hypokalaemia)
- Acid-base disturbances
- Laxative abuse → hypokalaemic, hyperchloraemic, non-anion gap metabolic acidosis
- Self-induced vomiting / diuretic abuse → hypokalaemic metabolic alkalosis
Initial Assessment and Referral
Bulimia nervosa can be a medical emergency mainly due to purging behaviour.
First, assess whether the patient requires immediate emergency admission for inpatient care
- Key assessment / investigations
- Physical examination + observations
- BMI or weight (including rate of weight loss)
- U&Es for electrolyte levels
- ECG
- Key indications for immediate emergency admission for inpatient care:
- Clinically unstable
- Severe dehydration
- Severe electrolyte disturbances (e.g. severe hypokalaemia)
- ECG showing
- Significant QTc prolongation
- Arrhythmias
If immediate emergency is NOT necessary → refer immediately to a community-based, age-appropriate eating disorder service
If an eating disorder places the patient’s physical health at serious risk, but they refuse necessary inpatient treatment, consider compulsory treatment under the appropriate legal framework
- Adults: see the Mental Health Act (MHA) 1983
- Children and young people: see the Mental Health Act (MHA) 1983 or the Children Act 1983
Management
Do NOT offer pharmacological management to treat bulimia nervosa itself
Pharmacological management might be appropriate to manage comorbidities (e.g. depression)
Children and Young People (<18 y/o)
| Management component | Description |
|---|---|
| Psychological therapy | 1st line: bulimia-nervosa-focused family therapy
Alternative (if bulimia-nervosa-focused family therapy is not appropriate):
|
| Ongoing physical health monitoring | Risk-based physical monitoring (applicable for all eating disorders):
Regular dental review is necessary for bulimia nervosa |
| Identifying and treating comorbidities | Including:
|
Adults
| Management component | Description |
|---|---|
| Psychological therapy | 1st line: bulimia-nervosa-focused guided self-help
Alternative (if bulimia-nervosa-focused guided self-help is not appropriate):
|
| Ongoing physical health monitoring | Risk-based physical monitoring (applicable for all eating disorders):
Regular dental review is necessary for bulimia nervosa |
| Identifying and treating comorbidities | Including:
|