Obesity is one of the most important preventable diseases in the UK . The best measure of obesity is body mass index (BMI).
Classification BMI (weight in kg ÷ (height in m):
- 18.5–24.9 Healthy weight
- 25–29.9 Overweight
- 30–34.9 Obesity I
- 35–39.9 Obesity II
- >40 Obesity III (Morbid obesity)
Waist circumference. Alternative measure of body fat correlated with CHD risk, DM, hyperlipidaemia, and i BP. Measured halfway between the superior iliac crest and the rib cage. Use in addition to BMI to aid assessment of health risks.
• Physical inactivity
• Smoking cessation—mean weight i 3–4kg
• Cultural factors
• Low education
• Polygenic genetic predisposition—71 in 3 obese people—more prone to obesity again after successful dieting
• Childbirth—especially if not breastfeeding.
• Drugs—steroids, antipsychotics (e.g. olanzapine), contraceptives (especially depo-injections), sulfonylureas, insulin
• Endocrine causes (rare)—hypothyroidism, Cushing’s syndrome, PCOS—only investigate if there are other symptoms/signs of endocrine disease
• Ongoing binge eating disorder.
Prevention Begins: in childhood with healthy patterns of exercise/diet.
Management: When the body’s intake > output over a period of time, obesity results. Management aims to reverse this trend on a long-term basis through healthy diet, adjustment of calorie intake, physical exercise, and psychological support.
Initial assessment : Assess willingness to change, eating behaviour and diet, physical activity, psychological distress, and social and family factors affecting diet. Check a baseline BMI and waist circumference. Check BP, blood glucose, and fasting lipid profile.
Advice: Whether willing to change or not, provide advice on risks of obesity, and benefits of healthy eating and physical exercise. Tailor your advice to the individual. If unwilling to change, reinforce this information at each encounter with the patient.
Diet: Advise a weight loss diet for any patient who is overweight/obese and willing to change:
• Low calorie diets All obese people lose weight on a low-energy intake. Aim for weight loss of 1–2lb (0.5–1kg)/wk using a decrease in calorie intake of 7600kcal/d with a target BMI of 25, in steps of 5–10% of original weight. There is no health benefit of weight decrease below this. If simple diet sheets are not effective, refer to a dietician
• Very low calorie diets (<1,000kcal/d). Only limited place in management—use for a maximum of 12wk for obese patients when weight loss has plateaued
Drug therapy BNF 4.5.1. Orlistat (120mg tds with food) is the only drug licensed for treatment of obesity in the UK. It acts by decrease fat absorption. Consider if a 3mo trial of supervised diet/exercise has failed and BMI ≥30kg/m2 or ≥27kg/m + co-morbidity (e.g. DM, increase BP). Continue treatment >3mo only if weight d is ≥5% of initial body weight.
Surgery Consider if BMI >40kg/m2 and non-surgical measures have failed. Adjustable gastric banding is the most common procedure. Complications: band slippage/damage; gastric erosion, pouch dilatation; infection; malabsorption.
Group and behavioural therapy group activities, e.g. Weight Watchers, have a higher success rates in producing/maintaining weight decrease. Behavioural therapy together with low calorie diets is also effective.
Maintenance of weight loss Once a patient has lost weight, continue to monitor diet. Ongoing follow-up helps to sustain weight loss. Weight fluctuation (yo-yo dieting) may be harmful.