If you’re overweight, and dieting and exercise haven’t worked for you, your doctor might recommend a weight loss program. This could include diet pills such as Orlistat, which is sometimes sold under the brand name Xenical.

According to the NHS, ‘many different types of anti-obesity medicines have been tested in clinical trials, but only one has proved to be safe and effective: Orlistat.’

Xenical / Orlistat capsules

Xenical & Orlistat weight loss medication

Xenical/Orlistat is the most extensively studied pharmacological weight management treatment to date. It is the only available weight loss medication that works locally in the gut to prevent dietary fat absorption by around 30 per cent to effectively promote weight loss.

Orlistat should be used as part of a lifestyle that also includes diet, exercise, and weight management. Your daily intake of fat, protein, and carbohydrates should be evenly divided over all of your daily meals, with the ultimate goal being gradual, sustainable weight loss.

You can buy Orlistat here at PostMyMeds.

What does Orlistat do to your body?

Orlistat is taken at mealtimes to prevent fat that is eaten in the meals from being broken down and absorbed by the body. This means the body cannot use the fat as a source of energy, or convert it into fat tissue.

Orlistat is not absorbed into the bloodstream, but works locally in the gut by blocking enzymes which digest fat, specifically preventing the action of two enzymes called gastric and pancreatic lipases that are found in the digestive juices. These enzymes normally break down fats that we consume in our diet into molecules that are small enough to be absorbed from the gut and into the bloodstream.

Nearly a third of the fat that you eat is blocked by Orlistat. The undigested fat is not absorbed into your body and is passed out in your stools (faeces). It is recommended that you reduce your fat intake to 30% of your total calorie intake whilst taking Orlistat.

weight loss large jeans

What Orlistat dose should I take?

The normal Orlistat mg dose is one capsule – 120 mg, three times a day with each meal. However, you do not need to take one if there is no fat in the meal or if you miss a meal.

One orlistat capsule is taken with water immediately before, during or up to one hour after, each main meal (up to a maximum of three capsules a day). If you miss a meal, or the meal doesn’t contain any fat, you shouldn’t take the orlistat capsule.

Treatment with orlistat should only continue beyond three months if you’ve lost 5% of your body weight. It usually starts to affect how you digest fat within one to two days.

If you haven’t lost weight after taking orlistat for three months, it’s unlikely to be an effective treatment for you. Consult your doctor or pharmacist, as it may be necessary to stop your treatment.

What are the side effects of Orlistat?

Although Orlistat is a long established medication it may not be suitable for everyone. In some patients it should not be used at all, while others should use with caution. You should always read the patient information leaflet of Orlistat before taking it to ensure it is safe for you.

Common side effects of orlistat include:

  • fatty or oily stools
  • needing the toilet urgently
  • passing stools more often
  • an oily discharge from your rectum/oily spots on your underwear
  • flatulence
  • stomach pain
  • headaches
  • upper respiratory tract infections/colds

It is worth noting that these side effects are much less likely to occur if you stick to a low-fat diet.

Women who are taking the pill (the oral contraceptive) should use an additional method of contraception when taking Orlistat if they experience diarrhoea, because the pill might not be absorbed properly.

Orlistat may interfere with the absorption of fat-soluble vitamins (A, D, E and K), so patients are recommended to take a daily multivitamin as part of their diet while they’re still taking this medication. The multivitamin should be taken 2 hours after taking Orlistat or before going to bed.

Weight loss may also affect the dose of pharmaceutical medications taken for other conditions (e.g. high cholesterol or diabetes), and losing weight may mean you need to adjust the dose of these medications. To gain the maximum benefit from Orlistat you should follow the nutrition program recommended to you by your doctor. As with any weight-control program, over-consumption of fat and calories may reduce any weight loss effect.

If you have questions or queries about weight loss medications from PostMyMeds don’t hesitate to get in touch via our website. Our trained clinicians are always happy to help.

Although all of our content is written and reviewed by healthcare professionals, it should not be substituted for or used as medical advice. If you have any questions about your health, please speak to your doctor.

Authored Jan 17, 2019 by Thomas Hall
Reviewed Dec 14, 2021 by Prabjeet Saundh, MPharm