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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)

Table O1Classification of obesity

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


  • 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).



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