What to Know About Alli (Orlistat)

A Lipase Inhibitor Approved for Weight Loss

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Many diet pills help you lose weight by decreasing your hunger or boosting your energy levels. Alli, which contains 60 milligrams (mg) of orlistat, works a little differently. This over-the-counter diet pill is designed to assist with weight loss by acting as a lipase inhibitor.

The term "lipase inhibitor" means that it blocks some of the fat you eat from being absorbed into your body, instead, eliminating it in your stool. When less fat is absorbed and stored, it may become easier to slim down.

Uses

The U.S. Food and Drug Administration (FDA) approved Alli for over-the-counter use in 2007. The FDA adds that this approval is specifically for "overweight adults, 18 years and older."

On its website, Alli clarifies that this diet pill was designed for people with a body max index (BMI) of 25 or higher. This aligns with the Centers for Disease Control and Prevention's definition of being overweight, which is a BMI of 25.0 to 29.9, with a BMI of 30.0 or above classified as obese.

Both the FDA and Alli further state that this weight loss aid should be used in combination with a reduced calorie, low-fat diet. So, if you're looking for a diet pill that allows you to eat what you want (and however much you want), Alli is not approved for this purpose.

It is always recommended that you consult a medical professional before making any changes to your diet, exercise plan, or lifestyle to learn whether it is safe given your health and medical conditions.

Effectiveness

On its website, Alli states that it "can help you lose 10-15% of your visceral fat or 'belly fat' vs placebo after 24 weeks of use." If you go to its Frequently Asked Questions page, it names four studies that it says "have examined the efficacy and safety of alli capsules (60 mg orlistat)."

To be clear, the four studies referenced did not look at the effects of Alli specifically, but the orlistat it contains. In each study, some of the subjects did take 60 mg of orlistat, which is the same amount in the Alli capsules. They also all reported positive results with regard to weight loss but, again, this was attributed to orlistat, not to Alli specifically.

One study that did involve the Alli brand was published in 2017. However, it didn't look at its weight loss potential but, rather, whether fecal fat excretion is increased when it is taken with flaxseed or dairy calcium. It found that it is, and that this tends to increase diarrhea severity.

The main question this leaves is, because Alli is to be used in conjunction with a reduced calorie, low-fat diet, is it more effective for weight loss than diet alone? Research seems to support that the answer is yes for orlistat, but fails to make a connection directly to the Alli brand.

Before Taking

It is always recommended that you consult with your doctor before using an over-the-counter weight loss aid. This gives you the opportunity to discuss whether it is safe for you based on your physical health and condition.

Precautions and Contraindications

Alli's precautions and contraindications can be separated into two categories: people who should not use this weight loss pill at all and those who should inquire about its safety prior to use.

Who Should Not Take Alli

Alli's packaging specifically states that it should not be used by certain individuals. This includes:

  • Those who have had an organ transplant (because orlistat interferes with anti-rejection medicines)
  • People who take cyclosporine, a drug that is sometimes used as an anti-rejection medication but can also be used to treat immune system disorders
  • Individuals who have been diagnosed with a condition in which the body's ability to absorb food is somehow reduced or limited
  • People who are not classified as being overweight
  • People under the age of 18
  • People who are allergic to orlistat or any other ingredients in Alli

The site's Frequently Asked Questions website page adds that this weight loss pill should also not be used by people who are pregnant or breastfeeding. It also recommends that Alli not be used by people following a low-carb, high-fat diet.

Who Should Inquire About Alli's Safety

There are also certain individuals for whom Alli may potentially be unsafe, warranting a discussion with your doctor before using. This includes:

  • People who have ever had issues with their gallbladder, pancreatitis, or kidney stones
  • People taking anticoagulants, or blood-thinning medications
  • People taking heart medications
  • People taking medication for diabetes
  • People taking medication for thyroid disease
  • People taking antiretrovirals
  • People taking medications for seizures
  • People taking any other weight loss products

When taking these other medications, the manufacturer recommends speaking with your doctor because some of these medications may need to be adjusted when also taking orlistat.

Other Lipase Inhibitors

Alli isn't the only FDA-approved lipase inhibitor on the market. In 1999, the FDA also approved Xenical. The main difference between Xenical and Alli is that Xenical requires a prescription, likely because it contains twice as much orlistat at 120 mg.

Dosage

According to the manufacturer, each Alli capsule contains 60 mg of orlistat. It recommends taking one capsule with each meal that contains fat (the site specifically recommends consuming between 12 grams and 18 grams of fat per meal), but not exceeding three capsules daily.

The manufacturer further indicates that the Alli capsule should be taken within an hour of each meal—whether before, during, or after—and that there should be at least two hours in between doses.

All listed dosages are according to the drug manufacturer. Talk to your doctor to make sure you are taking the right dose for you.

Modifications

The only modification suggested by the manufacturer is when a particular meal contains no fat. In this case, it says that the Alli dosage can be skipped.

How to Take and Store

The manufacturer recommends taking one Alli capsule with each meal that contains fat, not to exceed three capsules daily. It also suggests taking a multivitamin daily (at bedtime) since Alli may reduce the body's ability to absorb fat-soluble vitamins.

Alli capsules should be stored at temperatures between 68 degrees and 77 degrees Fahrenheit, and protected from excessive light and humidity. If the product has spent long periods in temperatures exceeding 86 degrees, the manufacturer suggests discontinuing its use.

Alli's product label indicates that, in the case of an overdose, you should seek medical attention or contact a Poison Control Center immediately.

Alli Side Effects

Some people experience side effects when taking Alli.

Common

If you eat more fat than recommended while taking Alli, you may experience difficulty controlling your bowel movements, oily stool, and stomach problems. Generally, these effects occur when starting Alli (during the first few weeks), often reducing over time.

Severe

The U.S. National Library of Medicine reports a few potentially serious side effects sometimes associated with taking orlistat. Among them are:

  • Hives, rash, or itching
  • Trouble breathing or swallowing
  • Abdominal pain that is severe or unrelenting (doesn't ease up)
  • Excessive fatigue or weakness
  • Nausea, vomiting, or loss of appetite
  • Yellow eyes or skin
  • Dark urine
  • Light stools

If any severe side effects are experienced, it is recommended that you seek medical attention immediately.

Warnings and Interactions

The one major concern with regard to orlistat is that it may potentially injure the liver, with some case studies suggesting a causal connection (that the liver injury was a direct consequence of taking the orlistat).

Other research stresses that these effects are relatively rare and, overall, this drug "has a good safety profile." Similar studies have analyzed the drug's effect on liver function and reached a similar conclusion, citing that liver injury cannot be excluded as a possibility, though it is not likely.

If any major issues are experienced when taking Alli, its use can be discontinued immediately. That makes it unlike some other medications where it is recommended that you slowly reduce your dosage. With Alli, you can simply stop taking it.

A Word From Verywell

Before you consider any diet pill, you should evaluate your diet history and your weight loss barriers. You should also talk to your doctor about weight loss. Alli is available over the counter, so no prescription is necessary. But that doesn't mean that anyone should take it.

Certain dieters, including those who have had an organ transplant or have food absorption issues, are advised not to take Alli. Alli might also not be right for people who take certain medications or have had issues with their gallbladder, pancreas or kidney stones.

If you have gained weight or have trouble losing weight because you have difficult food cravings, Alli may not help. Since Alli does not suppress appetite, you may not get the weight loss help you need from this pill.

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Article Sources
Verywell Fit uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
  1. U.S. Food and Drug Administration. Orlistat (marketed as Alli and Xenical) information. Reviewed Jul 08, 2015.

  2. Centers for Disease Control and Prevention. About Adult BMI. Reviewed Sep 17, 2020.

  3. Alli. Who should take Alli?

  4. Alli. Frequently asked questions.

  5. Kristensen M, Juul S, Sorensen K, Lorenzen J, Astrup A. Supplementation with dairy calcium and/or flaxseed fibers in conjunction with orlistat augments fecal fat excretion without altering ratings of gastrointestinal comfort. Nutr Metab. 2017;14(13). doi:10.1186/s12986-017-0164-8

  6. MyAlli.com. Product information.

  7. U.S. National Library of Medicine. Orlistat. Revised Jan 15, 2016.

  8. Sall D, Wang J, Rashkin M, Welch M, Droege C, Schauer D. Orlistat-induced fulminant hepatic failure. Clin Obes. 2014;4(6):342-7. doi:10.1111/cob.12075

  9. Sumithran P, Proietto J. Benefit-risk assessment of orlistat in the treatment of obesity. Drug Saf. 2014;37:597-608. doi:10.1007/s40264-014-0210-7

  10. Morris M, Lane P, Lee K, Parks D. An integrated analysis of liver safety data from orlistat clinical trials. Obes Facts. 2012;5:485-94. doi:10.1159/000341589

Additional Reading
  • Alli. Alli.

  • U.S. National Library of Medicine, Medline Plus. Orlistat. Revised Jan 15, 2016.