Obesity

The WHO definition of obesity is an abnormal or excessive accumulation of body fat that may impair health. It is regarded as a global health epidemic and a chronic disease. The outstanding cause of weight gain in exogenous obesity is excessive calorie intake coupled with lack of exercise. Useful measuring instruments include:

• body mass index (BMI): ‘healthy’ range is between 20 and 25

  (BMI = weight (kg) ÷ height (m²))

• abdominal obesity—defined as a waist:hip circumference ratio (W/H ratio) of >0.85 in women and >0.95 in men—which is a better predictor of cardiovascular risk and other complications of obesity than BMI

• waist circumference: risk of comorbidity ♂ >94 cm; ♀ >80 cm; high mortality risk threshold ♂ 102 cm; ♀ 88 cm

• single skinfold thickness (>25 mm suggests increased body fat)

Management principles (WHO and NHMRC)

1. Reduction in energy intake

2. Change in diet composition, including fat intake to <30% calorie intake

3. The DASH diet (designed for hypertension) and the Mediterranean diet have good evidence for nutritional value and sustainability

4. Increased physical activity (e.g. walking 30 min/d or 10 000 steps/d [use pedometer])

5. Behavioural therapy

Rules

• Need a close supportive relationship: encourage behaviour change

• Promote realistic goals—lose weight slowly

• Follow a healthy fat, high-fibre, reduced calorie intake (low sugar) diet

• Allow normal foods with reduced quantity and frequency (e.g. eat ⅓ less than usual)

• Supportive counselling (never judgmental)

• Provide a list of ‘tips’ for coping

• Advise keeping a food, exercise and behaviour diary

• Strict follow-up (e.g. fortnightly, then monthly) until goal weight achieved, then 3 mthly reviews

Pharmacotherapy (adjunct therapy) Adverse effects can be problematic. Consider for those with BMI >30 and failed well-supervised lifestyle measures. The agents are:

• local, acting on GIT:

  • – bulking agents (e.g. methylcellulose)

  • – lipase inhibitors—orlistat (Xenical) 120 mg (o) tds ac (used with a low-fat eating program); the only NHMRC currently registered treatment agent

• centrally acting agents (not recommended):

  • – amphetamine derivatives (reduce hunger)

  • – phentermine 15–40 mg (o)/d (limited use)

• serotonin analogues (enhances satiety)

  • – fluoxetine 20–40 mg (o)/d

  • – sibutramine 10–15 mg (o)/d (monitor BP)

  • – sertraline 50–100 mg (o)/d

Bariatric (gastric) surgery Consider referral for surgical intervention (e.g. Lap Band, sleeve gastrectomy and Roux-en-Y bypass)—perhaps the most effective treatment for significant obesity. It is recommended in those with a BMI >40 or >35 with severe comorbidities, especially diabetes (good evidence).