Definition of Obesity
- Obesity: Excess adipose tissue that impairs health.
- Classification by Body Mass Index (BMI)
- Underweight: <18.5 kg/m²
- Normal weight: 18.5–24.9 kg/m²
- Overweight: 25.0–29.9 kg/m²
- Class I Obesity (Obese): 30.0–34.9 kg/m²
- Class II Obesity (Moderately obese): 35.0–39.9 kg/m²
- Class III Obesity (Severely obese): 40.0–49.9 kg/m²
- Class IV Obesity (Super morbidly obese): ≥50 kg/m²
- Ethnic-Specific Considerations: In Asian populations, a BMI ≥23 kg/m² is considered overweight, and ≥30 kg/m² is obese.
Prevalence & Impact
- Epidemic: Over 66% of U.S. adults are overweight/obese.
- Associated Morbidity: Increased risk for type 2 diabetes, hypertension, dyslipidemia, cardiovascular disease, certain cancers, obstructive sleep apnea, and joint disease.
- Mortality: Higher in obese individuals due to cardiovascular and metabolic complications.
Clinical Assessment
- Body Mass Index (BMI)
- Surrogate measure of total body fat.
- May overestimate body fat in very muscular individuals.
- Waist Circumference
- Estimates central (visceral) fat distribution.
- Cutoffs for increased cardiometabolic risk:
- Men: >102 cm, Women: >88 cm.
- Asian Men: >90 cm, Asian Women: >80 cm.
- Waist-Hip Ratio
- Men: >0.9, Women: >0.85 indicative of abdominal obesity.
- History
- Age of onset, dietary habits, physical activity, past weight-loss attempts, medication review, comorbidities.
- Physical Exam
- Blood pressure, signs of sleep apnea, evidence of Cushing syndrome or hypothyroidism (if suspected).
- Laboratory Tests
- Fasting plasma glucose, lipids.
- Additional testing for suspected conditions (e.g., overnight oximetry for obstructive sleep apnea).
Etiology
- Lifestyle: Excess caloric intake, sedentary behavior.
- Medical Causes (rare):
- Cushing syndrome,
- Hypothyroidism,
- Hypothalamic lesions.
- Medications:
- Corticosteroids,
- Some antipsychotics,
- Antidepressants,
- Certain antiepileptics,
- Thiazolidinediones,
- Insulin.
Management Goals
- Health Improvement: Reduce obesity-related comorbidity risk.
- Weight Reduction: Aim for ~10% weight loss over 6 months.
- Long-Term Maintenance: Key to preventing regain.
Treatment Approaches
- Lifestyle Modifications
- Dietary Intervention:
- Calorie reduction (balance deficit ~500–750 kcal/day),
- Emphasize fruits, vegetables, fiber, lean proteins,
- Reduce dietary fat (20–30% of calories),
- Limit sugar-sweetened beverages.
- Physical Activity:
- ≥30 min/day moderate-intensity isotonic exercise,
- Increase daily steps (pedometer).
- Behavior Therapy:
- Journaling (food/exercise logs),
- Stress management,
- Goal setting,
- Stimulus control,
- Cognitive restructuring.
- Dietary Intervention:
- Pharmacotherapy
- For patients with BMI ≥30 or ≥27 with obesity-related comorbidities.
- Agents vary (e.g., appetite suppressants, malabsorption inducers).
- Bariatric Surgery
- For severe obesity (BMI ≥40 or ≥35 with comorbidities).
- Various procedures (restrictive, malabsorptive, or both).
Indications for Surgery
- Patient Eligibility
- Class IV obesity: BMI ≥50 kg/m² (super morbid obesity)
- Class III obesity: BMI ≥40–49.9 kg/m² (severe obesity)
- Class II obesity: BMI ≥35–39.9 kg/m² with serious obesity-related conditions
- Effectiveness
- Most effective treatment for clinically severe obesity
- Average 30–35% total body weight loss, maintained in ~60% at 5 years
- Resolves or improves many comorbidities (diabetes, obstructive sleep apnea, hypertension, hyperlipidemia, fatty liver)
- Contraindications
- Binge eating disorder
- Substance abuse (drugs/alcohol)
- Major depression/psychosis
- High anesthetic risk from other medical disorders
- Inability to adhere to postoperative dietary guidelines
Surgical Approaches
- Restrictive Procedures
- Limit stomach capacity and slow gastric emptying; small-intestine absorption largely intact.
- Examples:
- Laparoscopic Adjustable Gastric Banding
- Silicone band placed near gastroesophageal junction
- Diameter adjusted via subcutaneous reservoir
- Fewer metabolic issues; purely restrictive
- Sleeve Gastrectomy
- Partial gastrectomy removing greater curvature
- Creates narrow tubular stomach (“sleeve”)
- Reduced ghrelin production → lower appetite
- Laparoscopic Adjustable Gastric Banding
- Restrictive–Malabsorptive Procedures
- Combine small gastric pouch + re-routing of intestine → mild to moderate malabsorption
- Examples:
- Roux-en-Y Gastric Bypass (RYGB)
- Small gastric pouch (<30 mL)
- Roux limb of small intestine attached to pouch
- Mild malabsorption, dumping syndrome
- Can be done laparoscopically (faster recovery)
- Biliopancreatic Diversion
- Partial gastrectomy + long segment intestinal bypass
- More malabsorption, higher risk of nutritional issues
- Biliopancreatic Diversion with Duodenal Switch
- Variation preserving the pylorus
- Less diarrhea & stomal ulceration vs. standard diversion
- Roux-en-Y Gastric Bypass (RYGB)
Complications & Nutritional Management
- Operative Risk
- Overall mortality <1%
- Reoperation or endoscopic dilation for strictures
- Common Postoperative Issues
- Stoma stenosis or marginal ulcers (~15%): Presents with nausea/vomiting, dysphagia to solids
- Nutrient Deficiencies (particularly with combined malabsorptive procedures):
- Iron, calcium, folate
- Vitamins B12, D, E
- Protein malnutrition in extreme cases if dietary compliance is poor