Medication

This section is aimed at healthcare professionals

Pharmacological treatment should only be considered after dietary, exercise and behavioural approaches have been started and evaluated. Drug treatment should be considered for patients who have not reached their target weight loss or have reached a plateau on dietary, activity and behavioural changes alone. The decision to start drug treatment, and the choice of drug, should be made after discussing with the patient the potential benefits and limitations, including the mode of action, adverse effects and monitoring requirements, and their potential impact on the patient's motivation.

When a drug treatment has been prescribed, arrangements should be made for appropriate healthcare professionals to offer information, support and counselling on additional diet, physical activity and behavioural strategies. Information on patient support programmes should also be provided.

Pharmacological treatment may be used to maintain weight loss, rather than continue to lose weight. If there is concern about the adequacy of micronutrient intake, a supplement providing the reference nutrient intake for all vitamins and minerals should be considered, particularly for vulnerable groups such as older people (who may be at risk of malnutrition) and young people (who need vitamins and minerals for growth and development).

People whose drug treatment is being withdrawn should be offered support to help maintain weight loss, because their self-confidence and belief in their ability to make changes may be low if they did not reach their target weight.

Regular review is recommended to monitor the effect of drug treatment and to reinforce lifestyle advice and adherence. Withdrawal of drug treatment should be considered in people who do not lose enough weight. Rates of weight loss may be slower in people with type 2 diabetes, so less strict goals than those for people without diabetes may be appropriate. These goals should be agreed with the person and reviewed regularly.

The two most commonly prescribed medications for diet and exercise-resistant obesity are:

  1. Orlistat (Xenical), which reduces intestinal fat absorption by inhibiting an enzyme called lipase in the pancreas.
  2. Sibutramine (Reductil), which has an effect on chemicals in the brain, neurotransmitters leading to an increase in your satiety levels.

Weight loss with these drugs is modest; over the long-term average weight loss on orlistat is 2.9 kg and on sibutramine is 4.2 kg. Another anti-obesity medication called rimonabant can lead to a 4.7 kg weight loss.

Orlistat and rimonabant lead to a reduced incidence of diabetes. All three drugs have some effect on lipoproteins (which is the form in which cholesterol travels in the blood). There is little data, however, on longer-term complications of obesity such as heart attacks. All drugs have side effects and potential contraindications (specific situations where the drug should not be used). It is common for weight loss drugs to be tried for a period of time (e.g. 3 months), and to discontinue them or change to another agent if no benefit is achieved, such as where weight loss is less than 5% of the total body weight.

What is the scientific evidence?

A meta-analysis of randomised controlled trials by the international Cochrane Collaboration concluded that in diabetic patients fluoxetine, orlistat and sibutramine could achieve significant but modest weight loss over 12-57 weeks, with long-term health benefits being unclear.

Obesity may also influence the choice of drug treatment for diabetes. Metformin may lead to mild weight reduction (as opposed to sulfonylureas and insulin), and has been demonstrated to reduce the risk of cardiovascular disease in type 2 diabetics who are obese. The thiazolidinediones may cause slight weight gain, but decrease the 'pathologic' form of abdominal fat and may therefore be used in diabetics with central obesity.

Orlistat

Orlistat should be prescribed only as part of an overall plan for managing obesity in adults who meet one of the following criteria:

  • a BMI of 28.0 kg/m2 or more with associated risk factors
  • a BMI of 30.0 kg/m2 or more.

Therapy should be continued beyond 3 months only if the person has lost at least 5% of their initial body weight since starting drug treatment.

The decision to use drug treatment for longer than 12 months (usually for weight maintenance) should be made after discussing potential benefits and limitations with the patient.

Sibutramine

Sibutramine should be prescribed only as part of an overall plan for managing obesity in adults who meet one of the following criteria:

  • a BMI of 27.0 kg/m2 or more and other obesity-related risk factors such as type 2 diabetes or dyslipidaemia
  • a BMI of 30.0 kg/m2 or more.

Sibutramine should not be prescribed unless there are adequate arrangements for monitoring both weight loss and adverse effects (specifically pulse and blood pressure).

Therapy should be continued beyond 3 months only if the person has lost at least 5% of their initial body weight since starting drug treatment.

Treatment is not currently recommended beyond the licensed duration of 12 months.

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