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Prescription and over the counter medication for obesity

There is no miracle drug for losing weight. However, for people who are very overweight or obese, there is one drug that can help them lose some weight but only if they are also following a low- calorie diet and exercise programme.

The only clinically proven, safe and effective drug that can help an obese or very overweight person lose some weight is orlistat.

How does orlistat work?

Orlistat works by attaching itself to an enzyme called lipase, which the body needs to break down fat. Without the fat breaking down, your body cannot absorb it, so instead the fat travels through your intestines and is passed out in your stools (poo). This means that orlistat can help you stop gaining more weight, but it doesn't help you to actually lose weight already gained. In addition, if your meals are too high in fat when you take orlistat, they can cause unpleasant side effects (see below). For these reasons it is important that the person taking orlistat is already following an appropriate weight-loss diet.

Reviews of research studies have shown that people who took orlistat while also following a low- calorie diet lost an average of about 8.1kg (1.25 stone) after a year, about 2.8kg (6lb) more than those who did not take orlistat. Two-year studies have also shown that those taking orlistat in combination with a low-calorie diet can lose 10% of their body weight in 1 year.

Who can take orlistat?

Orlistat is not recommended for everyone. It can be prescribed when:

  • A person’s health is at risk due to their weight
  • Dietary, exercise and behavioural approaches have been started and evaluated
  • Body mass index (BMI) is 30 or higher, or BMI is greater than 28 and medical problems related to weight, such as hypertension or diabetes, also exist.

Orlistat is not recommended for people who are allergic or sensitive to any ingredients in the drug; for women who are pregnant or breast-feeding; for children or the elderly; or for people who have cholestasis, chronic malabsorption syndrome, epilepsy, hypothyroidism, or kidney or liver problems.

A prescription for orlistat will continue after 3 months only if you have lost 5% of your body weight, though the percentage may be slightly lower if you have type-2 diabetes, as it may take people with diabetes longer to lose weight. If your doctor is satisfied with your progress after 3 months, you may be prescribed orlistat for up to 1 year, at which point your doctor will need to review your progress.

Orlistat is also available over-the-counter (without a prescription) from a pharmacist, who is required to weigh you before selling the drug to you. The over-the-counter version is sold under the brand name ‘alli’ and contains half the prescription dose of orlistat. To purchase alli from a pharmacist, you must be:

  • 18 years old or older
  • Have a BMI of 28 or more
  • Be willing to start a low-calorie, lower fat diet

It is not recommended that you take alli for more than 6 months.

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