Obesity is a clinical condition characterised by an excess of body fat. The most common definition used is that it is present if the patient has a BMI greater than 30.
In the UK the prevalence is rising rapidly. In 1980, 8 per cent of women and 6 per cent of men were obese. By 2002, this had risen to 22 per cent for both genders and it is estimated that 12 million adults will be obese by 2010.
Obesity is strongly linked to type-2 diabetes and cardiovascular disease (CVD). It increases the risk of several cancers. Sleep apnoea is largely confined to the obese patient.
The BMI can be calculated from the patient's height and their weight.
However, this needs to be interpreted with caution because it can overestimate the health risk in groups such as athletes, who have low body fat, and underestimate the risk in patients of Asian origin.
Waist circumference better reflects the amount of high-risk abdominal and visceral fats. For men, a waist circumference of less than 94cm is low risk, 94-102cm is high risk and over 102cm is very high risk. For women, a waist circumference of less than 80cm is low risk, 80-88cm is high risk and over 88cm is very high risk.
Risk factors, such as smoking, alcohol and family history of obesity or co-morbidities, should be elicited.
It is equally important to explore the patient's view of their weight and the diagnosis; discuss their current eating patterns and physical activity levels. Find out what the patient has already tried and assess the patient's readiness and motivation to change.
The examination should include an examination of the thyroid, BP measurement and abdominal examination.
Investigations could include urinalysis, U&Es, TFTs, LFTs, fasting lipids and glucose. Other tests, including sex hormone profiles, glucose tolerance tests and cardiovascular investigations may be needed.
A multi-component approach to weight reduction is most likely to produce results.
It is important not to set unrealistic goals because this may discourage the patient. Realistic targets include a loss of 0.5-1kg per week with an overall aim of 5-10 per cent reduction from original weight.
Behavioural approaches, including social support groups, cognitive behavioural therapy, assertiveness training and problem solving can help with patient motivation.
Patients should be encouraged to do at least 30 minutes of moderate-intensity physical activity five times a week.
The type of activity should be something the patient enjoys and could include activities such as gardening. A step counter is another approach.
Diets should encourage healthy eating. Diets that reduce energy intake by 600kcal/day, or that work by lowering fat content, are associated with sustainable weight loss.
Very low-calorie diets (<1,000kcal/day) should be restricted to 12 weeks.
Patients need advice on how to maintain their weight after reaching their goal.
Drugs should be considered after diet, exercise and behavioural approaches have been tried. They also can be useful if weight loss has reached a plateau.
Three agents are currently available: orlistat, sibutramine and rimonabant.
All are effective both in reducing weight and associated cardiometabolic risk factors.
Referral for surgery should be considered for those with type III obesity who have not responded to non-surgical management.
Dr Spinks is a GP in Strood, Kent
- Obesity is associated with high morbidity from diabetes, CVD and cancer.
- The BMI is used to define obesity but this relates poorly to other risk factors. Waist circumference correlates well with cardiovascular risk.
- Aim for 0.5-1kg/week loss with a target of 5-10 per cent total reduction.
- Management includes behavioural change, exercise and dietary modification.
- Orlistat, sibutramine and rimonabant are effective at reducing weight and cardiometabolic risks.
- Referral for bariatric surgery may be the solution for a few patients, such as those with type III obesity.