Obesity

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

1. Body Mass Index (BMI)
   • Surrogate measure of total body fat.
   • May overestimate body fat in very muscular individuals.
2. 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.
3. Waist-Hip Ratio
   • Men: >0.9, Women: >0.85 indicative of abdominal obesity.
4. History
   • Age of onset, dietary habits, physical activity, past weight-loss attempts, medication review, comorbidities.
5. Physical Exam
   • Blood pressure, signs of sleep apnea, evidence of Cushing syndrome or hypothyroidism (if suspected).
6. 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

1. 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.
2. Pharmacotherapy
   • For patients with BMI ≥30 or ≥27 with obesity-related comorbidities.
   • Agents vary (e.g., appetite suppressants, malabsorption inducers).
3. 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

1. 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
2. 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

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