Weight Gain and Obesity

Introduction

Obesity is recognized by the Canadian Medical Association (CMA) and Obesity Canada as a complex, progressive, and relapsing chronic disease characterized by abnormal or excessive body fat (adiposity) that impairs health. For MCCQE1 preparation, it is crucial to move beyond simple BMI calculations and understand the pathophysiology, the Edmonton Obesity Staging System (EOSS), and the 5 As of Obesity Management.

In Canada, the prevalence of obesity has been steadily increasing, with approximately 1 in 4 Canadian adults living with clinical obesity. This has significant implications for public health and the burden of chronic disease management.

Classification and Epidemiology

Body Mass Index (BMI)

While BMI is a population-level screening tool, it does not directly measure health or adiposity distribution.

Edmonton Obesity Staging System (EOSS)

The MCCQE1 frequently tests the ability to determine prognosis. The EOSS is a Canadian-developed staging system that is a better predictor of all-cause mortality than BMI alone.

• Stage 0: No apparent risk factors (e.g., normal BP, lipids, glucose), no physical symptoms, no psychopathology.
• Stage 1: Subclinical risk factors (e.g., borderline hypertension, impaired fasting glucose), mild physical symptoms, mild psychopathology.
• Stage 2: Established chronic disease (e.g., hypertension, T2DM, sleep apnea), moderate limitations involved.
• Stage 3: End-organ damage (e.g., heart failure, diabetic complications), significant functional impairment.
• Stage 4: Severe disability (e.g., end-stage renal disease), severe functional limitations.

Etiology and Pathophysiology

Obesity is multifactorial. It is rarely just “calories in vs. calories out” due to complex neurohormonal regulation (leptin, ghrelin, GLP-1).

Clinical Assessment: The 5 As

The 2020 Canadian Adult Obesity Clinical Practice Guidelines recommend using the 5 As framework.

Diagnostic Investigations Checklist

• TSH: Rule out hypothyroidism.
• Fasting Glucose / HbA1c: Screen for Pre-diabetes/Diabetes.
• Lipid Profile: Dyslipidemia screening.
• Liver Enzymes (ALT/AST): Screen for MAFLD (Metabolic Associated Fatty Liver Disease).
• Creatinine/eGFR: Renal function.
• Consider: 24h urinary free cortisol (if Cushingoid features present).

Management Strategies

Management is tiered based on severity and patient preference.

1. Medical Nutrition Therapy & Physical Activity

• Nutrition: There is no single “best” diet. The Mediterranean diet has strong evidence for cardiovascular health. Follow Canada’s Food Guide (plenty of vegetables/fruits, protein foods, whole grains, water).
• Activity: Aim for 150 minutes of moderate-to-vigorous aerobic activity per week + resistance training 2x/week.

2. Psychological Intervention

• Cognitive Behavioral Therapy (CBT) for weight management.
• Address Binge Eating Disorder (BED) if present.

3. Pharmacotherapy

Indicated for BMI ≥ 30 kg/m², or ≥ 27 kg/m² with adiposity-related complications.

4. Bariatric Surgery

The most effective long-term treatment for severe obesity.

• Indications:
  • BMI ≥ 40 kg/m².
  • BMI ≥ 35 kg/m² with at least one obesity-related comorbidity (e.g., T2DM, HTN, OSA).
• Types: Roux-en-Y Gastric Bypass (Gold standard), Sleeve Gastrectomy.
• Post-op: Requires lifelong vitamin supplementation (B12, Iron, Calcium, Vit D).

Canadian Guidelines (Obesity Canada 2020/2022)

The Canadian Adult Obesity Clinical Practice Guidelines represent a paradigm shift in obesity management. Key takeaways for MCCQE1:

1. Obesity is a Chronic Disease: It is not a lifestyle choice.
2. Focus on Health: Treatment goals should focus on improving health parameters (BP, A1c, Mobility, Quality of Life) rather than cosmetic weight loss.
3. Individualized Care: Treatment must be tailored to the root causes (e.g., treating depression, changing obesogenic meds).
4. Long-term Management: Like hypertension or diabetes, obesity requires lifelong management; stopping treatment usually leads to weight regain.

Key Points to Remember for MCCQE1

• Definition: Obesity is defined by adiposity that impairs health, not just BMI.
• Staging: Know the Edmonton Obesity Staging System (EOSS). A patient with BMI 32 and T2DM (Stage 2) has higher mortality risk than a patient with BMI 40 and no comorbidities (Stage 0/1).
• Waist Circumference: Vital sign for metabolic risk. ≥ 102cm (M) / ≥ 88cm (F) for Caucasians.
• Pharmacotherapy: Liraglutide and Semaglutide are first-line GLP-1 agonists. Naltrexone/Bupropion is contraindicated in seizure disorders and uncontrolled HTN.
• Surgery: Indicated for BMI ≥ 40 or ≥ 35 + comorbidity.
• Secondary Causes: Always screen for Hypothyroidism and consider Cushing’s if clinical features align.
• Language: Always use “Person-first” language (“Patient with obesity”).

Sample Question

A 46-year-old woman presents to her family physician for follow-up regarding weight management. She has a Body Mass Index (BMI) of 33 kg/m². She has a history of pre-diabetes and knee osteoarthritis. Despite adhering to a structured nutritional plan and engaging in 150 minutes of moderate aerobic activity weekly for the past 6 months, she has only lost 1 kg. She is frustrated and concerned about her future health. Her blood pressure is 128/78 mmHg.

Which one of the following is the most appropriate next step in management?

• A. Refer immediately for Roux-en-Y gastric bypass surgery
• B. Initiate pharmacotherapy with Liraglutide
• C. Advise the patient to reduce caloric intake to 800 kcal/day
• D. Reassure the patient and continue current lifestyle modifications for another 6 months
• E. Initiate pharmacotherapy with Desmopressin

Explanation

The correct answer is:

• B. Initiate pharmacotherapy with Liraglutide

Explanation: This patient has Class I obesity (BMI 30-34.9) with obesity-related complications (pre-diabetes, osteoarthritis). According to the Canadian Adult Obesity Clinical Practice Guidelines, pharmacotherapy is indicated for individuals with a BMI ≥ 30 kg/m² or ≥ 27 kg/m² with adiposity-related complications, who have not met weight loss goals with lifestyle modifications alone. Liraglutide is a GLP-1 receptor agonist approved by Health Canada for chronic weight management and would be an appropriate intensification of treatment.

• Option A: Bariatric surgery is generally indicated for BMI ≥ 40 kg/m² or BMI ≥ 35 kg/m² with comorbidities. This patient’s BMI is 33, so she does not currently meet the standard Canadian criteria for surgery.
• Option C: Very Low Calorie Diets (VLCD) < 800 kcal/day are generally not recommended for routine weight management without specialist supervision due to risks of gallstones and electrolyte abnormalities, and they have high rates of weight regain.
• Option D: The patient has already tried lifestyle modification for 6 months with minimal success and is experiencing complications. Clinical inertia should be avoided; intensification is warranted.
• Option E: Desmopressin is an antidiuretic used for diabetes insipidus and bedwetting; it has no role in obesity management.

References

1. Obesity Canada. (2020). Canadian Adult Obesity Clinical Practice Guidelines (CPGs). Retrieved from https://obesitycanada.ca/guidelines/ 
2. Wharton S, et al. (2020). Obesity in adults: a clinical practice guideline. CMAJ, 192(31), E875-E891.
3. Lau DCW, et al. (2007). 2006 Canadian clinical practice guidelines on the management and prevention of obesity in adults and children. CMAJ, 176(8), S1-13.
4. Medical Council of Canada. (2023). MCCQE Part I Clinical Decision-Making and Multiple-Choice Question Objectives.
5. Health Canada. (2023). Canada’s Food Guide.