About This Page
This is a clinician-written, evidence-based guide aligned to the MCC Examination Objectives. It is structured by clinical presentation — the way the MCCQE tests and the way patients actually present. Management reflects current Canadian guidelines (CMA, CFPC, CPS). Always cross-reference with institutional protocols and clinical judgment.
Key points
- Eating disorder presentations are medically risky: check vitals, orthostatic changes, weight trajectory, ECG, electrolytes, and purging behaviours
- Must-not-miss complications include bradycardia, hypotension, syncope, hypokalaemia, prolonged QTc, dehydration, refeeding syndrome, suicidality, and pregnancy
- The differential includes anorexia nervosa, bulimia nervosa, binge-eating disorder, ARFID, depression/anxiety/OCD, substance use, endocrine/GI disease, malignancy, and abuse/neglect
- Family-based treatment is first-line for many children/adolescents with anorexia nervosa; adults require coordinated psychological, nutritional, and medical care
- Do not be reassured by normal BMI: bulimia, atypical anorexia, purging, and rapid weight loss can be medically dangerous at any weight
Approach to the Presentation
Weight loss or abnormal eating behaviours may present as amenorrhoea, fainting, vomiting, dental erosion, compulsive exercise, bingeing, purging, constipation, fatigue, or parental concern. Ask about weight trajectory, desired weight, fear of weight gain, body image, restriction, binge episodes, vomiting, laxatives/diuretics, exercise, diet pills, insulin omission, menstrual history, sexual health, pregnancy, trauma, bullying, social media, family conflict, depression, anxiety, OCD, self-harm, and substance use. Examine hydration, orthostatic vitals, bradycardia, hypothermia, BMI percentile in paediatrics, pubertal status, dental/parotid changes, lanugo, oedema, and muscle wasting.
Differential Diagnosis
| diagnosis | likelihood | key features | distinguishing test |
|---|---|---|---|
| Anorexia nervosa / atypical anorexia nervosa with medical instability | must-not-miss | Restriction, fear of weight gain, body image disturbance, rapid weight loss, bradycardia, hypotension, hypothermia, amenorrhoea | Clinical diagnosis + vitals/ECG/electrolytes and growth/weight trajectory |
| Bulimia nervosa with electrolyte/QT risk | must-not-miss | Binge eating with compensatory vomiting/laxatives/diuretics/exercise, dental erosion, parotid enlargement, calluses, normal weight common | Electrolytes, metabolic alkalosis, ECG QTc, clinical history |
| Refeeding syndrome risk | must-not-miss | Severely malnourished or rapid weight loss; weakness, oedema, arrhythmia, delirium after nutrition increase | Phosphate, potassium, magnesium, glucose; monitor during refeeding |
| Suicidality / severe depression comorbidity | must-not-miss | Hopelessness, self-harm, substance use, perfectionism, shame, social withdrawal | Direct suicide risk assessment |
| Binge-eating disorder | common | Recurrent binge episodes with loss of control and distress without regular compensatory behaviours | Clinical DSM-5-TR criteria; assess metabolic complications and mood |
| ARFID | common | Restriction due to sensory sensitivity, fear of choking/vomiting, or low interest in food without body image disturbance | Clinical history; growth/weight and nutritional assessment |
| Depression/anxiety/OCD-related appetite or eating change | common | Low appetite, nausea, contamination fears, emetophobia, compulsive rituals, no core drive for thinness in some cases | Mood/anxiety/OCD assessment |
| Endocrine disease | less common | Hyperthyroidism, diabetes, adrenal insufficiency; weight loss with tremor, polyuria, pigmentation, hypotension | TSH, glucose/A1c, electrolytes, cortisol if indicated |
| GI disease / malignancy / chronic infection | less common | Diarrhoea, blood in stool, fever, night sweats, abdominal pain, dysphagia, lymphadenopathy, fatigue | CBC, inflammatory markers, coeliac testing, stool tests, imaging/endoscopy as indicated |
Red Flags & Key History
Symptoms
Syncope, chest pain, palpitations, severe weakness, confusion, seizures
Rapid weight loss, refusal of fluids, persistent vomiting, laxative/diuretic abuse, insulin omission
Suicidal ideation, self-harm, severe depression, substance use
Pregnancy or postpartum eating disorder symptoms
Abuse, coercive control, bullying, safeguarding or neglect concerns
Fear of weight gain, body checking, calorie counting, compulsive exercise
Binge episodes with loss of control and shame
Signs
Bradycardia, hypotension, orthostatic hypotension/tachycardia, hypothermia
Prolonged QTc, arrhythmia, electrolyte abnormality
Dehydration, oedema, lanugo, muscle wasting, delayed puberty
Dental enamel erosion, parotid enlargement, Russell sign
Normal BMI despite rapid weight loss or purging does not remove risk
Approach to Investigation
First-line
Vitals including orthostatic BP/HR, weight and growth trajectoryUse paediatric growth charts where relevant; assess rate of weight loss, not just current BMI
ECGBradycardia, QTc prolongation, arrhythmia, electrolyte-related changes
Blood testsCBC, electrolytes including potassium/bicarbonate, urea/creatinine, glucose, magnesium, phosphate, LFTs, TSH, ferritin/B12
Pregnancy test and urinalysis when relevantPregnancy changes risk and management; urinalysis may show ketones, dehydration, or infection
Second-line
Nutritional and psychiatric assessmentDietary intake, purging, exercise, bingeing, body image, mood, anxiety/OCD, trauma, substance use, suicide risk
GI/endocrine work-upCoeliac screen, inflammatory markers, stool tests, imaging/endoscopy, cortisol or diabetes testing when symptoms suggest non-psychiatric weight loss
Specialist
Eating disorder programme referralCoordinated medical, nutritional, psychological, and family work; urgent when medically unstable or paediatric
Hospital admissionMarked bradycardia, hypotension, hypothermia, syncope, electrolyte abnormality, prolonged QTc, dehydration, food/fluid refusal, severe psychiatric risk
Management Principles
Canadian Paediatric Society Eating Disorder Guidance + Health Quality Ontario Eating Disorders Quality Standard + DSM-5-TR1
Medical stabilisation
- Admit or arrange urgent care for unstable vitals, electrolyte abnormality, prolonged QTc, dehydration, syncope, hypothermia, severe malnutrition, or high psychiatric risk
- Monitor for refeeding syndrome in malnourished patients: phosphate, potassium, magnesium, glucose, fluid balance, and cardiac status
2
Psychological and nutritional care
- Children/adolescents: family-based treatment is commonly first-line for anorexia nervosa when feasible
- Adults: evidence-based psychotherapy such as CBT-E, interpersonal therapy, or dialectical approaches depending on diagnosis and comorbidity
- Dietitian-supported nutritional rehabilitation with realistic meal planning
3
Medication principles
- SSRIs may help bulimia nervosa and comorbid depression/anxiety, but are not primary treatment for weight restoration in anorexia nervosa
- Avoid bupropion in eating disorders due to seizure risk
Complications & Pitfalls
- Normal BMI trap: Atypical anorexia and bulimia can be medically dangerous despite normal weight.
- Missed hypokalaemia/QT prolongation: Purging can produce fatal arrhythmias.
- Refeeding syndrome: Phosphate can fall rapidly after nutrition restart.
- Bupropion risk: Avoid in eating disorders because of seizure risk.
MCCQE1 Exam Tips
- 1Eating disorder questions often ask admission criteria: unstable vitals, electrolyte abnormality, prolonged QTc, syncope, or food/fluid refusal
- 2Normal BMI does not exclude eating disorder or medical instability
- 3Bulimia clue: parotid enlargement, dental erosion, Russell sign, hypokalaemic metabolic alkalosis
- 4ARFID lacks body image disturbance; anorexia nervosa includes fear of weight gain/body image distortion
- 5Family-based treatment is high-yield for adolescents with anorexia nervosa
- 6Avoid bupropion in eating disorders due to seizure risk
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