Boots WebMD Partners in Health
Return To Boots

Diet health centre


BMJ Group Medical Reference


This information is for people with serious weight problems. It tells you about orlistat, a medicine used for weight loss. It is based on the best and most up-to-date research.

Does it work?

Yes. If you're very overweight or obese, a drug called orlistat could help you to lose a small amount of weight and keep it off. But orlistat has side effects. And it doesn't work by itself. You also need to change the way you eat and exercise.

What is it?

Orlistat is a drug that can help people who are obese lose weight. It stops your body absorbing some of the fat from the food you eat. About a third of the fat you eat passes straight out of your body in your stools.

You can get orlistat on prescription from your doctor. The brand name is Xenical. You can also buy orlistat from a pharmacist, without a prescription, under the brand name Alli. The pills you can buy yourself contain half the dose of the prescription version.

Orlistat comes as pills that you take at mealtimes, up to three times a day. If you're going to eat a meal that doesn't contain any fat, you should skip the dose of orlistat with that meal.

Your doctor may recommend orlistat if: [2]

  • Your weight is a risk to your health. This means that your body mass index (BMI) is 30 or more, or your BMI is 28 to 30 and you have medical problems because of your weight

  • You have been following a diet and exercise programme for at least one month, and have already lost at least 2.5 kilograms (5.5 pounds)

  • You are able to get advice and support from a local dietitian, practice nurse or GP.

You can buy orlistat from a pharmacist if:

  • You're 18 or over

  • Your BMI is 28 or more

  • You're willing to start a low- calorie, lower-fat diet.

Usually, people lose weight quite quickly when they take orlistat. But it doesn't work for everyone. Talk to your doctor or pharmacist if you haven't lost weight after 12 weeks. Whatever happens, you shouldn't take the over-the-counter version of orlistat for longer than six months. If you want to take it for longer, talk to your doctor.

How can it help?

Taking orlistat can help some people lose weight. It's difficult to say for sure exactly how much weight you'll lose if you take orlistat. Some people lose more weight than others. [103] [104]

After taking orlistat for a year, people lost about 8.1 kilograms (about 18 pounds) on average.

That was about 2.8 kilograms (6 pounds) more than people who took a dummy treatment (a placebo).

One summary of the research looked at results of studies comparing orlistat, sibutramine (no longer available), and rimonabant (no longer available) with a dummy ( placebo) treatment. It found that, in studies lasting at least one year, orlistat reduced weight by 2.9 kilograms (about 6 pounds) more than placebo, but sibutramine reduced weight by 4.2 kilograms (about 9 pounds) more than placebo, and rimonabant by 4.7 kilograms (about 10 pounds) more. But the studies didn't compare the drugs directly with each other, so we don't know for sure which works best. [105]

Last Updated: June 21, 2012
This information does not replace medical advice.  If you are concerned you might have a medical problem please ask your Boots pharmacy team in your local Boots store, or see your doctor.

Popular slideshows & tools on BootsWebMD

woman looking at pregnancy test
Early pregnancy symptoms
donut on plate
The truth about sugar addiction
smiling african american woman
Best kept secrets for beautiful hair
couple watching sunset
How much do you know?
nappy being changed
How to change your baby's nappy
woman using moisturizer
Causes and home solutions
assorted spices
Pump up the flavour with spices
bag of crisps
Food cravings that wreck your diet
woman with cucumbers on eyes
How to banish dark circles and bags
probiotic shakes
Help digestion
polka dot dress on hangar
Lose weight without dieting