Diabetes Medications and New Drugs

Orlistat (Xenical)

What is Orlistat (Xenical)?

Orlistat is a drug used to promote weight loss in people who are overweight.

How does Orlistat work?

Orlistat works by blocking the action of chemicals called enzymes which break down fat.  Fats in our diet cannot be absorbed unless broken down in this manner to smaller components known as fatty acids.  Orlistat prevents this breakdown of fat and the undigested fat is passed in the stool. This drug does not suppress appetite.  It works within the gut and is not absorbed into the bloodstream.

How much weight can I lose with Orlistat?

The weight loss can be variable.  Orlistat will only work if you follow a program of diet and exercise.  Weight loss should be gradual and sustainable.  If you are obese, the health benefits of weight loss result from losing even 5-10% of your current body weight and you do not require dramatic weight reduction.

What are the side effects?

The main side effects are related to lack of absorption of dietary fat which results in an ‘oily diarrhoea’.  Flatulence, sometimes with ‘oily spotting’ is common. These effects depend on how much excess fat there is in your diet. It is the fat in your diet rather than the Orlistat which causes these effects.

Should I take Orlistat?

The indications for prescribing Orlistat are fairly rigid and your doctor is unlikely to prescribe this medication unless clearly indicated. If you are overweight with a body mass index of 27 kg/m2 and have diabetes you may qualify to receive this drug, but remember it is no ‘quick-fix’. Whichever anti-obesity medication you may use, there is simply no substitute for a proper diet and exercise, in order to lose weight.  Orlistat is only prescribed to people who have shown ability to comply with a suitable diet. All the details of prescribing cannot be described in this leaflet and we recommend you discuss this furhter with your doctor if necessary.

How is Orlistat taken?

Orlistat is available in 120 mg capsules. One capsule is taken with each meal or up to one hour after the meal is consumed. It is recommended that the total amount of daily fat is distributed evenly between your meals. If there is little or no fat in your meal you may skip the dose.

How long does it take to work?

Weight loss is usually seen within 2-4 weeks.

How long can I take it for?

It is not essential that you continue to take Orlistat once you have achieved the desired weight. Ideally you should aim to maintain your weight through diet and exercise.

Are there any precautions I should take?

Some of the fat-soluble vitamins may be poorly absorbed. It is worth taking a supplement of itamins A & D.  This dose is best taken at bedtime or more than two hours from your dose of Orlistat.

Who should not take Orlistat?

  • People who are not overweight
  • Pregnant or breastfeeding women
  • Children
  • Those unable to stick to a suitable diet !

What if I eat more than three meals a day?

Do not take more than three capsules of Orlistat per day.


Dr Nishan Wijenaike, Consultant Physician
West Suffolk Hospitals Diabetes Service
October 2002


Glucose Lowering drugs

Drugs for blood pressure

Cholesterol and other lipid lowering drugs

Drugs to lower cardiovascular risk

Drugs for neuropathic pain

Drugs which help weight loss

Drugs for erectile dysfunction

Drugs for Type 2 diabetes