The only medicines in the UK specifically licensed for the treatment of obesity are called orlistat and sibutramine. Orlistat works by reducing the absorption of the fat you eat. Sibutramine increases the feeling of fullness when you eat by boosting levels of the chemical, serotonin, which is naturally made in your body.
Both these drugs have been clinically proven to help people lose weight. They are 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 however 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 one- off small study, which 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 life-style 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.