How Alli Works to Help You Lose Weight

boxes of alli on a counter

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In This Article

Alli is an over-the-counter (OTC) diet pill approved by the U.S. Food and Drug Administration (FDA). It is the brand name for a medication called orlistat, which is perhaps better known by its prescription version's name Xenical. Alli is FDA-approved for use in overweight adults along with a reduced-calorie and low-fat diet as well as exercise. The diet pill is not an easy fix for weight loss, but it may help some people lose more weight and improve their health than lifestyle changes alone.

How Alli Works

Alli (orlistat) is a lipase inhibitor. It works by reducing the absorption of fat in your body. The diet pill claims that by taking the medication three times a day (one hour before, during, or after each meal), it will remove about 25 percent of the fat you consumed from your intestines.

Excess fat is eliminated from your body in your stool. But that doesn’t mean you can indulge in trans fats and other unhealthy foods when you take Alli. The medication should be used in conjunction with a well-balanced, low-calorie, and low-fat diet. It is also important that you consume healthy fats. You should aim for 15 grams of fat per meal, which means that you’ll eat less than 30 percent of your total daily calories from fat.

Alli contains 60 mg of orlistat, while Xenical contains 120 mg of the drug and requires a prescription from your healthcare provider.


How much weight you can lose when you take Alli depends on a number of factors, including recommended lifestyle changes.

If you don't adhere to the recommended healthy diet and lifestyle, you probably won’t lose weight. And if you don’t also exercise on a regular basis, any weight you do lose probably won’t stay off for good.

As researchers study weight loss with orlistat, the results have been mixed. A 2007 review found that participants who took a 60 mg dose of orlistat lost an average of 5 percent of their initial total body weight in four months. In 2009, the study was cited by GlaxoSmithKline (the company that makes Alli), when it launched the drug in Europe.

Another study published in 2015 tracked over 100,000 orlistat users over a three-year period. Researchers found that although patients lost just shy of a pound and a half per month during the first few months, they did not maintain significant weight loss for the long term.

Side Effects

According to the U.S. National Library of Medicine, the most common side effects of Alli involve changes to your bowel movements. They range from gas and loose or oily stools, to stomach cramps, oily spotting on your underwear, and difficulty controlling your bowel movements.

Many Alli users who complain about side effects experience them in response to eating a high-fat meal, but even with a careful diet, some users can have problems.

Side effects generally subside after the first few weeks of taking the pill. If Alli side effects continue beyond that point, talk to your doctor.

Risks and Warnings

In addition to side effects, Alli may be harmful to your liver. In 2010, the FDA updated its requirements for the labeling of orlistat products to include safety information about a few cases of severe liver injury linked to the weight-loss pill. If you have a pre-existing liver condition or experience jaundice, severe itching, or dark urine, see your doctor.

As with all medications, take caution to purchase Alli from a reputable vendor and check the package closely before taking a pill. In 2014, product tampering was reported and resulted in a voluntary recall of the diet pills. Alli came back on the market in 2015 with updated tamper-resistant packaging that makes it easier to see if the bottle has been opened.

Is It Right for You?

If you are thinking about taking Alli for weight loss, talk to your doctor. While a prescription is not required, you should not take orlistat if you have any of the following diagnoses:

  • Pregnancy
  • Cholestasis
  • Malabsorption syndrome
  • Anorexia nervosa
  • Bulimia
  • Diabetes
  • Kidney stones
  • Pancreatitis
  • Gallbladder disease
  • Thyroid disease

Your doctor is the best person to determine if the product is safe for you and how losing weight might improve your health.

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Article Sources
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