Orlistat: Minimising side effects

Orlistat can be a great ally in losing weight, as it expels up to a third of the fat you eat. In turn, this can help you to lose up to 50% more weight than through diet and exercise alone.

As with all medicines, Orlistat does have some side effects, which in most cases are very temporary. However, the risk of experiencing these side effects can be reduced with the right know-how. Read on to find out how orlistat works, and what you can do to ensure your weight loss journey is smooth sailing.

The science

The fat in your diet is normally broken down by enzymes in your stomach and intestines, before being absorbed into your body to be stored. Orlistat interferes with this process by blocking those enzymes, preventing around a third of the fat you eat from being absorbed by your body. Instead, it runs straight through the digestive system and is then passed out through the bowels.

The side effects

The main side-effects experienced with Orlistat are caused by the excess fat which is passed out by your body. Some users may experience fatty stools, an urgency to get to the toilet, and excess wind, which isn’t what anyone wants. Don’t worry though – the risk of these side effects can be minimised:

Minimising risk

Orlistat can only work effectively with a certain amount of fat per meal – if you eat more than 15 grams of fat, you might experience Orlistat’s side effects. So, to reduce your risk, you just need to ensure each meal does not exceed 15 grams of fat.

Although it may sound tricky, keeping track of the fat content in your meals can actually be very straightforward. Apps like My Fitness Pal contain huge databases full of nutritional information, for practically every food product you can think of – you can even scan barcodes and save recipes!

You can also reduce Orlistat’s side effects by sticking to the correct dosage of Orlistat. Although it may seem like taking more will help you lose weight quicker, that’s not the case. Instead, this will increase the likelihood of side effects, without any benefit to your treatment.


Scott McDougall (MPharm) is a clinical pharmacist and in addition to being Cornerstone’s senior in-house pharmacist, is the co-founder of The Independent Pharmacy, one of the UK’s leading independent online pharmacies.

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