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.
Orlistat is a medication that’s approved by the Food and Drug Administration (FDA) for weight loss. It’s one of the only over-the-counter (OTC) weight loss medications approved by the FDA, meaning that it doesn’t require a prescription from a doctor.
Orlistat is the generic name for the medication, and the brand-name version is called either Alli or Xenical depending on dose. We will use these terms interchangeably throughout this article because they refer to the same active drug ingredient.
In this article we’ll review published medical studies on orlistat to provide our determination on whether it’s safe and effective for weight loss. We’ll explain side effects of the medication, review whether the generic or brand-name version is more likely to be effective, and share a real user's review of the drug.
Does Orlistat Work?
Orlistat has been proven successful for weight loss in numerous medical trials, as is required for FDA approval.
A clinical trial published in the Journal of the Academy of Nutrition and Dietetics tested orlistat for weight loss in a population of overweight U.S. soldiers. The study participants used 60 milligram (mg) capsules of orlistat (which is the same dosage as contained in Alli) three times daily, totalling a 180 mg dose per day.
By the end of the six month trial, the soldiers taking orlistat had lost 2.87 pounds more than those taking placebo pills. It’s worth noting that the soldiers weren’t obese, but they were slightly overweight (more than 2% above the percent body fat standard set by the military).
While this trial did show orlistat to be effective, these results are modest and relatively unimpressive in our opinion. An average weight loss of 0.5 pounds per month may not be worth the risk of pharmaceutical side effects. This rate of weight loss can be achievable through lifestyle changes.
A separate clinical trial on orlistat, published in 2012, reported more impressive results. This study included both overweight and obese patients who took orlistat 60 mg capsules three times daily for 24 weeks along with diet and exercise counseling. The patients using orlistat lost 15.7% of visceral fat (fat around organs) compared to visceral fat loss of 9.4% for patients taking placebo pills.
Those using orlistat lost an average of 10.25 pounds of fat overall, which is significant.
Orlistat has also been proven effective for patients who are only slightly overweight. A medical study published in 2006 examined the effects of 16 weeks of orlistat for patients who were categorized as “mildly to moderately overweight.” The dosage was 60 mg, three times per day which seems to be the research standard.
Patients in this trial were assigned to a restricted calorie diet and supplemented with either orlistat or a placebo pill. Both groups lost weight, but the group taking orlistat lost 2.54 pounds more, which if sustained would equate to an annual weight loss of 8.26 pounds more than using diet alone.
We will conclude from the available research that orlistat is effective for weight loss, and appears to be more effective for patients at a higher starting weight such as obese patients.
Is Orlistat 120 mg More Effective?
All of the research reviewed in the previous section used an orlistat dose of 60 mg per tablet, but the drug can also be prescribed at a dose of 120 mg per tablet. The branded version of orlistat at a 120 mg dose is called Xenical, and is only available with a prescription.
Patients are often curious about whether the higher orlistat dosage is more effective for weight loss.
While we cannot locate any medical studies directly comparing the weight loss outcomes of orlistat 60 mg versus orlistat 120 mg per tablet, this medical review reported that the drug has dose-dependent effects on weight. This means that the higher the dose, the more weight is lost on average, which would suggest that orlistat 120 mg is more effective for weight loss than orlistat 60 mg.
The researchers in the linked review concluded that orlistat 120 mg “represents the optimal dosage regimen.”
Since higher doses of pharmaceutical drugs tend to be associated with higher risk of side effects, it may be worthwhile for patients considering orlistat to start at the 60 mg dose, and only increase the dose if the starting dose is ineffective, but only a doctor can provide individualized dosage advice.
Orlistat Side Effects
The more common side effects of orlistat are relatively mild, but there is a small risk of severe side effects.
The most common side effect is oily stool (medical term “steatorrhea”), but this should be expected because the drug increases the excretion percentage of dietary fats.
A meta-study on orlistat and weight loss reports that patients who keep dietary fat intake under 60 grams (g) daily experience fewer gastrointestinal side effects such as diarrhea and abdominal pain.
The same study documents that there is a rare risk of acute kidney injury because orlistat can increase oxalate production, which is deposited in the kidneys.
The FDA has also reported that orlistat is associated with a small but increased risk of severe liver injury. Only 13 out of over 40 million patients reported experiencing this side effect.
The side effect profile of orlistat is relatively mild compared to some of the pharmaceutical drugs we’ve reviewed on Illuminate Health. The drug does not appear to carry a “black box” warning on its FDA label, which is required for medications with severe or life-threatening side effects.
Real User Reviews Orlistat for Weight Loss
One of the most popular YouTube reviews of orlistat for weight loss comes from a channel called "Crazy Cat Paigey" and has achieved over 260,000 views at the time of updating this article.
The video appears unsponsored and the creator shares her weight loss journey on orlistat:
How Does Orlistat Work?
We believe it’s important for patients to understand the mechanism of action of their medications, so they can notice trends about types of drugs that are effective or ineffective for their individual biochemistry.
Orlistat’s mechanism of action is to inhibit the production of certain proteins that break down fat consumed in the diet, as documented by StatPearls, which is one of the largest free medical databases in the U.S.
Patients taking orlistat excrete more fat in feces than they would otherwise, which results in a lower percentage of fat being absorbed and metabolized by the body. The StatPearls resource reports that around 30% less dietary fat is absorbed on orlistat than would be otherwise.
These effects are reversible, and when a patient stops taking orlistat their pancreatic and gastric proteins return to functioning as normal.
Should I Take the Branded Version of Orlistat?
As we’ve referenced multiple times throughout this article, orlistat is the term for the generic version of the drug and the brand-name versions are Alli and Xenical. Alli is the 60 mg OTC version and Xenical is the 120 mg prescription version.
We generally recommend that patients speak with their doctor about the generic form of pharmaceutical drugs, because research shows them to be just as effective as branded drugs but cheaper.
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.”
We cannot determine if generic orlistat is available in the U.S., but we would recommend that any patient recommended by their doctor to take Alli or Xenical ask about this availability.
Can I Take Orlistat With Antibiotics?
Patients are often curious about whether orlistat can be taken with antibiotics, since weight loss medications are typically taken daily and may overlap with an antibiotic prescription.
Orlistat's FDA label makes no reference that antibiotics are contraindicated, which suggests that users can take orlistat with antibiotics, but it would be good to double-check with a doctor.
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 orlistat; 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.
Orlistat User Reviews
Orlistat has been reviewed over 300 times on Drugs.com, which is a website where users of pharmaceutical medication can publish reviews of their experience.
Orlistat has an average rating of 7.3/10 for treating obesity on Drugs.com, which is one of the higher average ratings we’ve noted.
The top positive review of the drug is written by a user named “Gurlo” who claims the drug was successful for weight loss even without incorporating exercise:
“25, female, started off at 15st 7lbs or 99kg or 217lbs (I’m 5’7). Originally was looking for a quick fix but realistically when it comes to weight loss there isn’t one. I gained 70lbs in the last 4 years and finally realized how unhappy I was. 20 days in and I have lost 14lbs/6kg. I am strict on my diet, though to be honest haven’t done the recommended exercise. So I can only imagine how much I would have lost in that time.”
The top negative review is published by a user named “FairyGardens” who rated the drug 1/10 and claims it was 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.”