Disclaimer: None of the information in this article constitutes medical advice. All statements are merely the opinion of the writer(s). We recommend that patients follow their doctor’s guidance in regard to prescription medication.
Alli is a weight loss pill that’s available over-the-counter (OTC) which means that it doesn’t require a prescription from a doctor. The drug is approved by the Food and Drug Administration (FDA) for weight loss, and to our knowledge is the only FDA-approved weight loss drug available OTC.
The generic name for Alli is orlistat, and we will use these terms interchangeably throughout this article as they refer to the same active drug ingredient.
In this article we’ll review the medical research on Alli to give our take on whether the medication is safe and effective for weight loss. We’ll overview the side effects of the drug, explain whether the generic version is likely to be as effective, and share a real Alli user review.
Does Alli Work?
The active ingredient in Alli has been studied in many medical trials.
One clinical trial examined whether Alli could lead to weight loss in U.S. soldiers. Over 6 months of treatment, the soldiers lost 2.87 pounds of fat mass. The soldiers weren’t obese, but they were slightly overweight.
While this trial did prove that Alli caused weight loss to a statistically significant degree, we don’t consider the results to be very impressive. Less than 0.5 pounds of fat loss per month is not worth the potential for side effects in our opinion.
A separate medical study on Alli had more impressive results. This study had a trial population of overweight and obese patients who took Alli for 24 weeks. The patients taking Alli lost 15.7% of visceral fat (fat around organs) compared to visceral fat loss of 9.4% on patients taking placebo.
Those taking Alli lost 10.25 pounds of fat overall, which is significant.
Alli has also been proven effective for patients who are only slightly overweight. A clinical trial published in the Annals of Pharmacotherapy journal tested the effects of Alli taken over 16 weeks in patients who were categorized as “mildly to moderately overweight.”
Patients in this trial were placed on a restricted calorie diet and instructed to take either Alli or a placebo pill. Both groups lost weight, but the group taking Alli lost 2.54 pounds more, which equates to a potential annuallized weight loss of 8.26 pounds on Alli.
We will conclude from the available research that Alli is effective for weight loss in patients who are slightly overweight, moderately overweight and obese, as it has been proven to work in all three types of patient populations.
How Does Alli Work?
It’s important for patients to know how their drugs function in the body.
Alli weight loss pills work by inhibiting production of certain proteins that break down fat consumed in the diet, as documented by StatPearls which is a leading database of pharmaceutical medications.
Patients taking Alli excrete more fat than they would otherwise, and the above-linked review reports that around 30% less dietary fat is absorbed on Alli than would be otherwise.
These effects are reversible, and when a patient stops taking Alli their enzyme and endogenous protein production returns to normal.
Alli Side Effects
Most side effects of Alli are relatively minor and gastrointestinal in nature, but there is a small risk of severe side effects.
The most common side effect as reported by the previously-linked StatPearls database is oily stool (medical term “steatorrhea”), but this should be expected because the way Alli works is by increasing the excretion rate of dietary fats.
A medical review of Alli noted that patients who kept dietary fat intake under 60 grams (g) daily experienced fewer GI-related side effects. It may be beneficial to even split this 60 g daily fat dose down into smaller portions to reduce side effect risk further.
For example, a patient eating three daily meals may benefit from consuming 20 g fat at each meal rather than 50 g fat at one meal and 5 g fat at the other meals.
StatPearls documents that there is a rare risk of acute kidney injury because Alli can increase oxalate production, which is deposited in the kidneys.
The FDA has also reported that Alli use is associated with a small but increased risk of severe liver injury. Only 13 out of over 40 million patients experienced this side effect.
Alli Real User Review
One of the most popular reviews of Alli from a real user is published by a channel called "The Killen Clan" and has achieved over 45,000 views at the time of updating this article.
The video appears unsponsored and the creator shares her experience using Alli for weight loss after 3 weeks:
Should I Take Alli Generic?
The generic form of Alli is called orlistat. Both of these drugs have the exact same active ingredient.
We typically recommend that patients speak with their doctor about the generic form of drugs rather than the brand-name versions, because medical research has found both drug types to be equally effective.
A medical review published in the PLOS Medicine journal compared the efficacy of generic and branded drugs, and found that there was no difference: “use of generics was associated with comparable clinical outcomes to use of brand-name products.”
Doctors may be compensated by drug companies in some cases to recommend brand-name versions of drugs, but in our opinion this does not benefit the patient.
Alli User Reviews
At the time of updating this article, Alli has been reviewed 95 times on Drugs.com, which is an online resource that allows patients to publish personal reviews of medications they're taking. The average review rating is 6/10.
The top positive review is written by a user named "Donna" who claims that, along with dietary changes, Alli has aided her weight loss efforts:
"I'm following more of a high veggie and low any type of carb diet, PLUS the Alli and I am *finally* losing those darn menopause pounds that, literally, sneak up on you. What am I saying? Take Alli to help with weight loss but if it doesn't work, you need to keep working with your Physician to get the right combination of diet & exercise for Alli to work."
The top negative review comes from a user named "FairyGardens" who claims that a new formulation of the drug has made it ineffective:
"The new generation of Orlistat, sold over the counter as Alli, does NOT work. I was on Xenical when it first came out in the 1990's. It worked very well and the orange discharge was a daily thing. Now 4 months ago I purchased Alli over the counter. Paid $85 and was very disappointed to find out that I had wasted my money."
Our Weight Loss Supplement Recommendations
There exist several over-the-counter (OTC) weight loss supplements that don't require a prescription, and which have medical research backing.
We are not suggesting that these products are as effective as Alli; just that it may be worthwhile for an overweight patient to discuss these options with their doctor given their documented efficacy and lack of significant side effects. They may also be used in addition to prescription weight loss medication.
We recommend dietary fiber as a safe and effective weight loss supplement, especially when combined with caloric restriction.
A landmark medical study found that moderate caloric restriction (750 calories per day below baseline) combined with dietary fiber intake (a minimum of 20 grams per day) caused an average weight loss of 16.03 pounds over 6 months. That’s a pace of 32 pounds per year of weight loss in overweight individuals simply by adding fiber to a moderately-restricted-calorie diet.
The fiber supplement we recommend is SuperGut Fiber Mix. It contains a clean and effective formulation: a blend of three different types of unflavored dietary fiber and zero additive ingredients. It can be mixed into liquids or foods. Interested consumers can buy SuperGut fiber at this link.
We recommend using two fiber mixes per day, which provides 16 g of total fiber. Diet should provide the remaining fiber necessary to meet the 20 g minimum threshold.
Medium-chain triglyceride (MCT) oil is another dietary supplement which has been shown in clinical trials to cause weight loss.
MCT oil is quickly absorbed by the body and increases metabolic rate, which causes fat loss. A meta-study on MCT oil documented weight loss of 1.12 pounds over 10 weeks. This equates to a potential annualized weight loss of 5.84 pounds with MCT oil supplementation.
We recommend Bulletproof MCT Oil as our top MCT oil product, because it has a clean and effective formulation. The only ingredient is MCT oil derived from coconuts, and the product has no questionable additives. Interested consumers can buy Bulletproof MCT Oil at this link.
The effective dose range of MCT oil for weight loss (based on the medical review) is 1.7 g to 10 g per day. Bulletproof's MCT oil provides 14 g in one tablespoon, so around two-thirds of one tablespoon should be a maximally-effective dosage.
In 2014, Alli's manufacturer GlaxoSmithKline announced that it was recalling all Alli pills from the market due to potential tampering. The press release stated that some of the packages may have been tampered with and may contain inauthentic product.
Alli patients had reported opening the product and noting different shapes and colors of pills than that of the official product.
We haven't come across another medication that faced this issue in an Illuminate Health review.