The only medicine in the UK specifically licensed for the treatment of obesity is orlistat. Orlistat works by reducing the absorption of the fat you eat.
Orlistat has been clinically proven to help people lose weight. It is only prescribed if you are obese or your weight is causing you health problems. You will also have to show that you have seriously attempted to lose weight by diet, exercise etc.
There is very little evidence that over-the-counter slimming pills that you can buy at health food shops will help you lose weight. Occasionally, research evidence is quoted for over-the-counter slimming pills, but this is usually from a one-off small study that hasn't been repeated. Many over-the-counter slimming pills give you very little information about the ingredients and how they are supposed to work. They can also be expensive.
Over-the-counter pills often come with recommendations that you follow a calorie-controlled diet and take more exercise, so a change in lifestyle will help you to lose weight with or without the pills.
Weight loss pills that claim you will lose a lot of weight very quickly, while eating normally, won't work as this isn't possible. If they recommend cutting out certain foods, this may help you lose weight but you probably won't be following a safe balanced diet.
It's possible that some slimming pills could be harmful if you have a medical condition or you are on certain medication. For example, they may interfere with prescribed medication for an under-active thyroid if the slimming pill contains a thyroid-stimulating ingredient. To lose weight safely and sensibly, you need to change your eating habits and do exercise.
Note: Sibutramine (Reductil) used to be another medicine licensed in the UK for the treatment of obesity. However, in January 2010, the European Medicines Agency recommended that doctors should no longer prescribe the medicine due to safety concerns. Data from a study involving 10,000 patients who took medicines that contained sibutramine showed an increased risk of heart attack or stroke.
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