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Aug 24, 2023

Weight Loss

Weight Loss

Alli - An OTC medication for Weight Loss

What is Alli (Orlistat)?

Alli is a medication containing orlistat and the only FDA-approved over-the-counter medication for weight loss. This medication is intended for those who have previously attempted weight management through diet and exercise alone, and are now seeking pharmaceutical help.

Alli's approved for adults aged 18 and above with a BMI (Body Mass Index) of at least 27. BMI is a measure of body composition that considers both height and weight, used to determine the presence of obesity. Easily accessible online calculators are available for BMI calculation, and a useful reference chart can be found on the Alli packaging.

This medication is taken by mouth with each meal containing fat, a maximum of three times daily.

How Alli Works For Weight Loss

Alli works by targeting the enzyme called "lipases." These enzymes are responsible for breaking down the fats you consume into small particles, so they can be absorbed into your body for use and storage.

Alli temporarily stops the work of lipases in the stomach and intestine. This blocks the breakdown of some fats, preventing the body from absorbing them. These undigested fats get passed in bowel movements. Over time, this results in weight loss due to the calorie loss.

What to Expect

Alli claims to help people lose an additional 2–3 pounds for every 5 pounds you lose you lose from diet alone. Studies for Alli were done alongside a healthier diet and exercise as this is essential for aiding in weight loss alongside medication.

It is important to note that many people regain the weight when they stop taking Alli. This is why it is important to maintain a balanced diet and exercise even after stopping taking Alli, only using weight loss medication as way to boot the weight loss in the beginning of your journey.

Side Effects

Side effects with Alli are very common. Because the medication stops absorption of fat, most of these side effects are related to excessive fats in the intestines and stools.

  • Oily rectal leakage
  • Flatulence with bowel movements
  • Bowel movement urgency
  • Oily bowel movements
  • Increased bowel movements
  • Bowel incontinence

The less fat you consume while taking Alli, the fewer side effects you will have. While this also reduces the effects that Alli has, it also reduces the amount of oil in the gut to cause upset and oily stools.


There are many possible risks of taking Alli, and some individuals should not take the medication. It is important to be aware of the risks and how to minimize them, as well as which individuals should avoid the medication

  • Organ transplant

    Individuals who have had an organ transplant should not take Alli. The medications you take after an organ transplant may not work as well alongside Alli.

  • Pregnancy

    In general, weight loss medications are not recommended during pregnancy. There is limited information on the use of Alli during pregnancy, but due to possible harms it is strictly recommended to be avoided.

  • Risk of vitamin deficiency

    As this medication reduces the absorption of fat, some vitamins that are absorbed with fat are not taken into the body. Because of this, it is recommended to take a multivitamin containing fat-soluble vitamins (vitamins A, D, E, and K) while using Alli. The multivitamin should be taken at least 2 hours before/after Alli, to ensure proper absorption.

    The easiest way to do this is to develop a routine. Taking Alli with breakfast, lunch, and dinner and then a multivitamin right before bed is a routine that works well for most people.


Even though it is an over-the-counter medication, Alli is relatively expensive. A one-month supply of the medication typically costs $65.

There is also a prescription version of Alli, called Xenical, made with the same active ingredient “orlistat”. Xenical costs more, but it is a stronger medication (double the dose) and therefore may have increased effects and side effects.

Prices mentioned in this article are based on average retail price at major box chain pharmacy in the U.S. as of August 3, 2023.


  1. Alli Orlistat Label. Food and Drug Administration. (2007). Retrieved August 3, 2023, from
  2. Alli. GoodRx. (n.d.). Retrieved August 3, 2023, from

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