Dr Clare Morrison

Article by Dr Clare Morrison

Weight loss tablets – fact or fiction?

With the huge number of diet fads and miracle weight loss claims we are exposed to on a regular basis, it is very hard to know how to separate the fact from the fiction and avoid the fakes.

Modern medicines that your doctor prescribes to you or you can access in your pharmacy are based on high-quality research and regulated by the government. You are more likely to see an impact and remain safe if you use these regulated medicines and avoid the ‘miracle treatment’ claims.

One medication that is grounded in research and regulated by the UK authorities is a weight loss pill called orlistat which has been shown to support weight loss in the right circumstances.

What is orlistat?

Orlistat is an oral medication that is available in the UK in two doses; 60mg and 120mg. The 60mg dose is a pharmacy medication meaning it can be accessed through online and high-street pharmacies in the right circumstances. The 120mg dose is a prescription only dose, meaning it can only be accessed with a prescription from a qualified healthcare professional.

Orlistat is not designed to be taken over long periods of time and it should not be taken for longer than 6 months or continue to be taken if you can’t see any benefit after 12 weeks.

How does orlistat work?

When you eat food, your body breaks that food down in order to absorb it. This process is performed by small biochemical ‘machines’ called enzymes. For each type of food, your body produces a specific family of enzymes.

One of the most common types of food is fat, also known as lipids, which naturally occur in lots of the food we eat. To break down fats, your body produces an enzyme called a lipase.

Orlistat is a type of medication called an ‘inhibitor’, meaning it inhibits something from working. In the case of orlistat, it is designed to inhibit the lipase enzyme. By inhibiting the lipase enzyme, orlistat reduces the amount of fat that your body extracts from the food you eat.

Does orlistat work?

Orlistat has been proven to inhibit lipase enzymes in the stomach and small intestine, preventing the body from breaking fats down into the molecules that can be absorbed.

From the research done on orlistat, it is estimated that 60mg taken three times a day will reduce the amount of fat your body absorbs from your food by 25%, or one quarter.

This extra undigested fat is passed out in your faeces and you may notice this change 24-48 hours after you begin taking orlistat. This effect will pass when you stop taking this medication.

How to get the best results from orlistat?

Orlistat has been developed to support weight loss in someone who is eating a low calorie and low-fat diet and is exercising regularly.

You should not expect orlistat to offer any benefits if it is taken without any dietary changes or regular exercise.

To get the best results from orlistat, you should make a clear plan to adjust your diet and exercise routine before you begin taking the medication. It is also a good idea to set yourself a time-based goal, e.g. losing 5kg in 3 months and ask a friend or family member to help you achieve this.

If you stop taking orlistat, you should do your best to keep exercising and eating well, both of which will support your overall health regardless of orlistat.

You should stop taking orlistat if you haven’t seen any benefits after 12 weeks.

Who is orlistat suitable for?

Orlistat 60mg is for people who have a body mass index (BMI) of 28 or over. Orlistat 120mg is for people who have a BMI of 30 or over. The 120mg dose is a prescription only medicine.

Orlistat should not be taken by women who are pregnant or breastfeeding. Neither should orlistat be taken by someone who is also taking an anticoagulant (e.g. warfarin) or ciclosporin.

As with all medications, orlistat can cause unwanted side effects. You should read the Patient Information Leaflet before deciding to take orlistat.

Orlistat Patient Information Leaflet: https://www.medicines.org.uk/emc/product/6533/pil

Support from MedExpress

MedExpress is a UK registered, online pharmacy and doctor service which provides prescription and non-prescription medicines to people in the right circumstances. Click here to view the range of weight loss treatments that are available: https://www.medexpress.co.uk/clinics/weight-loss/


1. Alli 60mg (Orlistat). Summary of Product Characteristics. Available online: https://www.medicines.org.uk/emc/product/6533/smpc Accessed April 2019

2. Alli 60mg (Orlistat). Patient Information Leaflet. Available online: https://www.medicines.org.uk/emc/product/6533/pil Accessed April 2019


Dr Clare Morrison
Dr Clare Morrison
Experienced General Practitioner in Hampshire since 1995, with particular interest in Nutrition, Obesity and Smoking Cessation.
Originally published May 03 2019, updated July 08 2019