Weight Loss: Eating Disorders & Anorexia Nervosa

Introduction

Eating disorders are serious, biologically influenced mental illnesses associated with severe disturbances in eating behaviours and related thoughts and emotions. For the MCCQE1, understanding Anorexia Nervosa (AN) and significant weight loss is crucial, as these conditions carry the highest mortality rate of any psychiatric disorder.

As a future Canadian physician, you must demonstrate competency in the CanMEDS roles, particularly Medical Expert (diagnosis and management) and Health Advocate (navigating the Canadian mental health system and addressing stigma).

Classification of Eating Disorders

The DSM-5-TR categorizes eating disorders into several distinct diagnoses. Understanding the nuance between them is vital for the MCCQE1.

Anorexia Nervosa: A Deep Dive

Epidemiology and Etiology

• Prevalence: Approximately 0.5% to 4% of women in Canada; increasingly recognized in men.
• Onset: Typically adolescence (peaks at ages 14 and 18).
• Risk Factors:
  • Biological: Genetics (50-80% heritability), female sex.
  • Psychological: Perfectionism, anxiety disorders, obsessive-compulsive traits.
  • Social: Cultural pressure for thinness, participation in “lean” sports (ballet, gymnastics, running).

Clinical Presentation

Patients often present with non-specific symptoms or are brought in by concerned family members.

History

• Constitutional: Fatigue, cold intolerance, dizziness, syncope.
• Gastrointestinal: Bloating, constipation, abdominal pain.
• Endocrine: Amenorrhea (secondary), loss of libido.
• Dermatologic: Hair loss, dry skin, easy bruising.

Physical Examination Findings

Systemic Complications

Diagnosis and Screening

Screening Tool: SCOFF Questionnaire

A score of ≥ 2 indicates a likely eating disorder.

1. Do you make yourself Sick because you feel uncomfortably full?
2. Do you worry you have lost Control over how much you eat?
3. Have you recently lost more than One stone (14 lbs or 6.35 kg) in a 3-month period?
4. Do you believe yourself to be Fat when others say you are too thin?
5. Would you say that Food dominates your life?

DSM-5-TR Diagnostic Criteria for Anorexia Nervosa

1. Restriction of energy intake relative to requirements, leading to a significantly low body weight.
2. Intense fear of gaining weight or becoming fat, or persistent behaviour that interferes with weight gain.
3. Disturbance in the way in which one’s body weight or shape is experienced, undue influence of body weight on self-evaluation, or persistent lack of recognition of the seriousness of current low body weight.

Investigations

For the MCCQE1, you must know how to work up a patient to assess medical stability.

Laboratory Workup

• CBC: Pan-cytopenia.
• Electrolytes: Hypokalemia (vomiting/diuretics), Hypochloremic metabolic alkalosis (vomiting), Metabolic acidosis (laxatives).
• Glucose: Hypoglycemia.
• Albumin: Often normal initially (due to dehydration) but may be low.
• Liver Enzymes: Mild elevation (AST/ALT) due to starvation autophagy of the liver.
• Thyroid: “Euthyroid Sick Syndrome” (Normal TSH, Low T3/T4).
• FSH/LH: Low (Hypogonadotropic hypogonadism).

Other Tests

• ECG: Mandatory. Look for bradycardia, prolonged QTc, T-wave inversion.
• Bone Mineral Density (DEXA): Indicated if amenorrhea > 6 months.

Management

Management involves a multidisciplinary team (Physician, Dietitian, Psychotherapist).

1. Medical Stabilization & Refeeding Syndrome

The most critical acute complication to manage is Refeeding Syndrome. This occurs when nutrition is reintroduced to a starved patient.

2. Canadian Guidelines for Hospitalization

According to Canadian guidelines (e.g., NEDIC, BC Clinical Guidelines), admission is required if:

• Heart Rate < 40 bpm
• Blood Pressure < 90/60 mmHg or significant orthostatic drop
• Temperature < 36.0°C
• Glucose < 3.0 mmol/L
• Electrolyte imbalance (K+ < 3.0 mmol/L)
• QTc prolongation > 450 ms
• Failure of outpatient treatment
• Acute suicide risk

3. Psychotherapy

• Family-Based Therapy (FBT/Maudsley Method): First-line treatment for adolescents with AN.
• CBT-E (Cognitive Behavioral Therapy for Eating Disorders): First-line for adults.

4. Pharmacotherapy

• Medications have limited efficacy in the acute phase of Anorexia Nervosa.
• SSRIs: Ineffective at low weight. May be useful for comorbid anxiety/depression after weight restoration.
• Olanzapine: May be used adjunctively for severe resistance/agitation to promote weight gain (off-label).

Differential Diagnosis (Medical Causes of Weight Loss)

Always rule out organic causes before confirming a psychiatric diagnosis.

• Mnemonic: “WEIGHT LOSS”
  • W - Worry (Anxiety/Depression)
  • E - Endocrine (Hyperthyroid, Diabetes, Addison’s)
  • I - Infection (TB, HIV, Parasites)
  • G - Gastrointestinal (Malabsorption, Celiac, IBD)
  • H - Hypermetabolic state (Pheochromocytoma)
  • T - Tumour (Malignancy)

Key Points to Remember for MCCQE1

• Mortality: AN has the highest mortality rate of any psychiatric illness (cardiac arrest or suicide).
• Legal: Under Canadian Mental Health Acts, patients can be formed (involuntary admission) if they lack insight and their life is in danger, which is common in severe AN.
• Refeeding: Monitor Phosphate daily for the first week of refeeding.
• Bone Health: Oral contraceptives do not protect bone density in AN; weight restoration is the only effective treatment.
• Vomiting Labs: Hypokalemic, Hypochloremic, Metabolic Alkalosis.
• Laxative Labs: Metabolic Acidosis.

Sample Question

Clinical Scenario

A 19-year-old female university student is brought to the emergency department by her roommate who found her fainting. The patient reports feeling “fine” but admits to restricting her diet to apples and water for the past 4 months to “avoid the freshman 15.”

Vitals:

• Temp: 35.8°C
• HR: 38 bpm
• BP: 85/55 mmHg
• RR: 14/min
• BMI: 14.5 kg/m²

Physical Exam:

• Cachectic appearance
• Fine downy hair on arms and back
• Dry mucous membranes

ECG: Sinus bradycardia with a QTc of 460 ms.

Which one of the following is the most appropriate initial management step?

Options

• A. Referral for outpatient Family-Based Therapy (FBT)
• B. Prescribe Fluoxetine 20 mg daily
• C. Immediate hospital admission for medical stabilization
• D. Referral to a dietitian for a high-calorie meal plan
• E. Reassurance and discharge with close follow-up in 1 week

Explanation

The correct answer is:

• C. Immediate hospital admission for medical stabilization

Detailed Explanation: This patient presents with severe Anorexia Nervosa and meets multiple criteria for immediate hospitalization based on Canadian guidelines.

1. Hemodynamic Instability: Severe bradycardia (HR < 40 bpm) and hypotension.
2. ECG Changes: QTc prolongation (> 450 ms) puts her at risk for Torsades de Pointes.
3. Severe Malnutrition: BMI < 15 is considered extreme anorexia.

While Family-Based Therapy (A) is the treatment of choice for adolescents, this patient is medically unstable and requires inpatient stabilization first. Fluoxetine (B) is not effective at low body weight and does not address the acute medical crisis. Dietitian referral (D) is insufficient for a patient with hemodynamic instability. Discharge (E) is unsafe given the risk of cardiac arrest.

References

1. Medical Council of Canada. MCC Objectives for the Qualifying Examination Part I.
2. Couturier, J., et al. (2020). Canadian Practice Guidelines for the Treatment of Children and Adolescents with Eating Disorders. Journal of Eating Disorders.
3. American Psychiatric Association. (2022). Diagnostic and Statistical Manual of Mental Disorders (5th ed., text rev.).
4. Toronto Notes. (2023). Psychiatry Chapter: Eating Disorders.
5. BC Guidelines. (2013). Eating Disorders: Anorexia Nervosa and Bulimia Nervosa. https://www2.gov.bc.ca/gov/content/health/practitioner-professional-resources/bc-guidelines