By Dr. Asnat Raziel, bariatric surgeon specializing in obesity treatment, metabolic health and healthy longevity; Director of the Multidisciplinary Center for Obesity Treatment, Assia Medical, Assuta Ramat HaChayal, Tel Aviv
Xenical (orlistat): a treatment that works in the gut, not the brain
Xenical (orlistat) is one of the longest-established obesity treatments, and it works differently from every other obesity drug. Its active ingredient, orlistat, reduces the absorption of fat from food. As a result, it has no effect on the brain, on appetite or on hormones.
In addition, the drug is barely absorbed into the bloodstream. This makes it suitable even for patients who cannot take stimulant drugs or injections from the GLP-1 family.
How it works: blocking the lipase enzyme
In the digestive tract, an enzyme called lipase breaks down dietary fat so the body can absorb it. Orlistat blocks this enzyme. At a dose of 120 mg three times a day, about 30% of the fat in a meal is not absorbed and leaves the body in the stool.
The upshot is simple: fewer calories enter the body. However, the drug does not reduce hunger, so success depends on combining it with a balanced, low-fat diet.
What does the research show about Xenical (orlistat)?
The most important study of the drug is the XENDOS trial. It enrolled 3,305 adults with obesity and without diabetes, and it lasted four years. All participants also received guidance on a reduced-calorie diet and daily walking.
After four years, weight loss in the orlistat group was 5.8 kg, compared with 3.0 kg in the placebo group. What’s more, the rate of new-onset diabetes was 6.2% in the drug group, compared with 9.0% in the placebo group. In other words, the risk of diabetes fell by 37.3%.
The most striking effect was seen in participants with impaired glucose tolerance, a form of prediabetes. In this group, diabetes developed in 18.8% of patients on the drug, compared with 28.8% on placebo. Put another way, the risk fell by 45%.
Who is Xenical suitable for?
According to the European product information, treatment is intended for adults with a BMI of 30 or higher. It is also intended for people with a BMI of 28 or higher who have associated risk factors, together with a reduced-calorie diet.
Xenical is particularly suitable for:
- Patients with heart disease who cannot take stimulant drugs
- Older adults who take many medications and prefer a treatment that is not absorbed
- Patients who cannot tolerate the nausea caused by injections
- People who want to learn, in practical terms, to eat less fat
How to take it and dosing
Xenical comes in 120 mg capsules. Take one capsule with water, just before a meal, during it or up to one hour after. The maximum is three capsules a day, one with each main meal.
If you skip a meal or eat a meal with no fat, you can skip the capsule. A higher dose adds no benefit. In some countries, orlistat is also sold over the counter at a 60 mg dose under the name Alli.
Good to know: according to the product information, if you have not lost at least 5% of your body weight after 12 weeks, it is advisable to stop treatment and consider an alternative with your doctor.
Vitamins and Xenical (orlistat)
Because the drug reduces fat absorption, it may also reduce the absorption of the fat-soluble vitamins A, D, E and K. It is therefore a good idea to eat plenty of fruit and vegetables. In addition, if your doctor recommends a multivitamin, take it at least two hours after the capsule or at bedtime.
Side effects: what happens to the fat that isn’t absorbed?
The side effects are mainly related to fat leaving the body:
- Oily, frequent bowel movements
- Gas, sometimes with oily discharge
- Urgency to have a bowel movement
- Abdominal pain or discomfort
These effects are not dangerous, but they get stronger when a meal is high in fat. For this reason, the drug “teaches” patients to choose low-fat foods. Indeed, according to the product information, the effects lessen over time.
Rarely, liver injury and kidney damage from oxalate crystals have been reported. See a doctor if you experience extreme fatigue, yellowing of the skin or eyes, dark urine or lower back pain.
Who should not take the drug?
- Chronic malabsorption syndrome
- Cholestasis, an impairment of bile flow
- Breastfeeding
- Hypersensitivity to orlistat
Xenical (orlistat) and other medications
Orlistat may change the absorption of certain medications. First, it should not be combined with cyclosporine unless there is no alternative, and then only with close monitoring of blood levels. Second, in patients taking warfarin, INR should be checked more often.
In addition, clinical monitoring and an ECG are recommended with amiodarone. Cases of underactive thyroid have also been reported with levothyroxine, so it is best to take the two at different times. Patients with epilepsy should have their seizure frequency monitored. Finally, severe diarrhea may reduce the effectiveness of birth control pills.
Combining with other treatments
Xenical can be combined with other medications, such as Razin or Mounjaro. The combination makes it possible to address both hunger and the amount of fat absorbed. However, any combination requires medical follow-up.
The treatment works especially well as part of a comprehensive program: a personalized diet, physical activity, good sleep and support from a dietitian. You can read more in my articles on combined obesity treatment and on Xenical for weight loss.
Frequently asked questions about Xenical
Does Xenical reduce appetite?
No. The drug acts only in the gut, so it does not change how hungry you feel.
What should I do if I have a lot of digestive side effects?
Reduce the fat in your meals. Generally, a diet with about 30% of calories from fat, divided across three meals, reduces these effects.
Can it be used long-term?
Yes. In the XENDOS trial, participants took the drug for four years, with appropriate medical follow-up.
The bottom line
Xenical (orlistat) is a safe, proven treatment that is neither hormonal nor a stimulant. The weight loss is modest, but it comes with a reduced risk of diabetes, especially in people with prediabetes. That’s why it remains an important option in the obesity treatment toolbox.
The information in this article is general and does not replace personalized medical advice.
References
Xenical 120 mg hard capsules – Summary of Product Characteristics
