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Dr Clare Morrison

Article by Dr Clare Morrison

How Effective Is Orlistat?


If you’re thinking about losing weight, you may have heard about the medicine Orlistat. Common questions include: does Orlistat work and how effective is Orlistat? To answer these questions, it’s important to look at the results of clinical trial data.

How does Orlistat work?

Orlistat acts locally in the gut (intestine). It works by preventing enzymes (lipases) from breaking down fat in the gut and allowing it to pass through the body undigested. This in turn reduces the number of calories absorbed by the body. At  the recommended dose of 120 mg three times a day, Orlistat reduces fat absorption by 30 percent.                                                                                                    

Is Orlistat effective?

Orlistat has been extensively studied over many clinical trials. In clinical trial data, the average weight loss with Orlistat in comparison to placebo with diet, was 50 percent higher. So if you could lose 6 kg on a regular diet, you could lose up to 9 kg with Orlistat. Furthermore, it was shown that those taking Orlistat maintained weight loss better than in the placebo group. To get maximum effectiveness from Orlistat, one capsule should be taken with each main meal (a maximum of three capsules a day), before, during, or up to one hour after each meal. If you miss a meal or the meal does not contain any fat, you do not need to take the capsule.

How much weight will I lose with Orlistat?

Although Orlistat is an effective weight loss medicine, it is not a miracle weight loss pill. It is important that you  combine it with a  diet containing around 30 percent of calories coming from fat, along with doing more exercise. Your weight depends on how much energy you take in versus the amount of energy your body uses up. If you eat fewer calories than you burn up, you will lose weight because your body has to tap into its fat stores to get extra energy.  Orlistat is effective in preventing fat absorption from your diet which will help reduce you total calorie intake. It is advisable to cut down your dietary calories by about 500 calories per day. This will result in loss of 1 lb per week, which is a healthy weight loss.

Dr Clare Morrison
Dr Clare Morrison
Experienced General Practitioner in Hampshire since 1995, with particular interest in Nutrition, Obesity and Smoking Cessation.
Originally published September 12 2014, updated July 05 2019