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

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