Obesity

 

• Background

  Classification

  By BMI (kg/m2):

  • Overweight: ≥25.
  • Moderate obesity (class I): ≥30.
  • Severe obesity (class II): ≥35.
  • Very severe obesity (class III): ≥40.

  Causes

  • Primarily due to obesogenic environment, containing cheap, widely available, highly palatable, heavily marketed, calorie-dense food.
  • Small role for specific genes e.g. FTO.
  • Very rarely, an underlying endocrine cause is found e.g. hypothyroidism, Cushing's. Other symptoms are usually present.
  • 'Personal responsibility' or 'lack of willpower' are unhelpful as explanations and fail to explain most historical and cross-national variance in weight.

• Health risks of obesity

  • Cardiovascular: hypertension, high cholesterol, ischaemic heart disease, stroke.
  • Metabolic syndrome: type 2 diabetes, NAFLD.
  • Cancer: breast, colorectal, endometrial, cholangiocarcinoma.
  • Respiratory: obstructive sleep apnoea, obesity hypoventilation syndrome.
  • Gallstones
  • Osteoarthritis

• Management

  • Weight-loss diets fail to lead to long-term, sustained weight loss in most, but should nevertheless usually be the 1st line option. In general, structured group approaches like Weight Watchers are more effective than self-directed efforts.
  • Advise regular exercise, ≥150 minutes/week, which has health benefits even if, as is usually the cause, it has minimal effects on weight.
  • Consider orlistat and surgical options if lifestyle changes are ineffective.

• Orlistat

  Mechanism

  Lipase inhibitor that reduces GI fat absorption, reducing weight.

  Indications

  • BMI ≥30 and failure of behavioural approaches.
  • Consider stopping if <5% weight loss after 12 weeks.

  Side effects

  • Oily stool and anal leakage.
  • Flatulence
  • Abdominal distention and pain.
  • Faecal urgency/incontinence.

• Bariatric surgery

  Indications

  Failure of non-surgical interventions and:

  • BMI ≥40.
  • BMI ≥35 and obesity complication e.g. HTN, T2DM. Even consider at BMI ≥30 with T2DM.

  Approaches and efficacy

  • All approaches are superior to non-surgical approaches at reducing weight and associated complications.
  • Roux-en-Y gastric bypass (RYGB) and sleeve gastrectomy (SG) have similar efficacy.
  • Adjustable gastric banding (AGB) is less effective and now less commonly used.
  • Biliopancreatic diversion with duodenal switch (BPD-DS) is less widely available, but may be the most effective option in severely obese patients, at the expense of higher GI complication rates.
  • All can be done laparoscopically.

  Complications

  Early:

  • Usual surgical risks: bleeding, infection, DVT/PE, HAP.
  • RYGB: anastomotic leak.
  • AGB: stomal obstruction.
  • 30 day mortality is <1/1000.

  Late:

  • Altered bowel habits: diarrhoea, flatulence, and steatorrhea are common, especially with RYGB and BPD-DS, while constipation is commoner with AGB.
  • Micronutrient deficiencies: see below.
  • RYGB: anastomotic stenosis, small bowel obstruction, dumping syndrome, internal hernia, gallstones.
  • SG: gastric outlet obstruction, GORD.
  • AGB: band slippage, band erosion, constipation.

  Follow up

  Monitoring:

  • Regularly check FBC, U&E, and LFT for all.
  • Regularly check ferritin, folic acid, B12, calcium, vit D, PTH, zinc, and copper, for all but gastric banding.

  Supplementation:

  • Multivitamin for all.
  • Iron PO, B12 IM, and calcium + vit D, for all but gastric banding.
  • Folic acid only if deficient.

  Continue to monitor for obesity-related complications.