How To Reduce The Side Effects Of Orlistat

The majority of Americans are overweight or obese, making weight loss aids tempting to those on weight loss journeys. 

Orlistat is a weight loss medication used to help treat overweight and obesity. 

The common brand names for Orlistat are Alli and Xenical. 

Alli is non-prescription-strength and available over the counter, while Xenical is the prescription-strength version of Orlistat.

Orlistat was approved by the United States Food and Drug Administration in 1999, so it’s one of the older weight loss aids on the market (compared to the newer weight loss injectables like Wegovy and Saxenda).

Orlistat might be recommended for patients who are considered overweight (body mass index [BMI] of 25 or greater) or obese (BMI of 30 or greater), especially in the presence of health conditions like diabetes, high blood pressure, and other health problems that can be affected by your body weight.

But, like all medications, taking Orlistat can lead to side effects. Keep reading to learn what they are, how long they last, and how to get rid of them.

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What are the side effects of Orlistat?

Because Orlistat blocks the breakdown and absorption of fats, the most common side effects of Orlistat have to do with your stomach and bowel habits.

The most commonly reported side effects of Orlistat are:

  • Abdominal or stomach pain or discomfort
  • Back pain
  • Difficulty moving
  • Gas with leaky bowel movements
  • Inability to hold bowel movements
  • Increase in bowel movements
  • Loss of bowel control
  • Oily bowel movements
  • Oily spotting of underclothes

More rarely, you might experience a serious side effect that requires more prompt medical attention, such as signs of an allergy to Orlistat. 

Some of these potential side effects are:

  • Dark-colored urine
  • Difficulty breathing or swallowing
  • Excessive tiredness or weakness
  • Hives
  • Itching
  • Light-colored stools
  • Loss of appetite
  • Nausea
  • Pain in the upper right part of the stomach
  • Rash
  • Severe or continuous stomach pain
  • Vomiting
  • Yellowing of the skin or eyes

The reason Orlistat commonly causes digestive side effects is that your stool becomes fattier, which can be difficult for the muscles of your rectum to hold in. 

Fecal incontinence (not making it to the bathroom to have a bowel movement) can be common in people taking Orlistat, which can be upsetting and impact their quality of life.

How long do Orlistat’s side effects last? 

Side effects of Orlistat are the most common when you first start taking it. In most people, side effects start to go away after the first couple of weeks of taking it.

If Orlistat side effects persist beyond four weeks and they are significantly impacting your quality of life, you should consult your healthcare provider to come up with a plan. 

You might need to adjust your diet (more on that next), your dosage, or stop taking Orlistat altogether, depending on how severe the side effects are.

Are there any long-term side effects of Orlistat?

There aren’t any long-term side effects of Orlistat that are likely to occur. Once you stop taking Orlistat, your digestive system will likely return to normal, and the side effects of Orlistat should lessen in severity and go away.

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How to reduce the side effects of Orlistat

The two most effective ways to reduce the side effects of Orlistat are to take it as prescribed (not taking more than you should) and to adjust your diet.

So what kind of diet modifications can help? We’ll suggest some tips that are the most effective!

Reduce your fat intake

This is likely the most effective way to reduce Orlistat side effects. Since Orlistat blocks the fat you eat from being absorbed, that means that the more fat you eat, the more oily your stools will become.

By cutting back on fat, your stools shouldn’t be as oily, which can help minimize unpleasant side effects like leakage of oily stool. 

In addition, lower-fat foods are lower in calories, which can aid in weight loss.

Try cutting back on fat by reducing your intake of foods like:

  • Beef (primarily non-lean cuts with marbled fat or non-lean [20% fat] ground beef)
  • Butter
  • Cheese (in large amounts – cheese is a good source of protein and can be a part of a balanced and healthy diet)
  • Coconut (including coconut oil)
  • Ice cream
  • Fried foods (battered, breaded, etc.)
  • Lamb
  • Lard and cream
  • Non-lean cuts of pork
  • Palm oil and palm kernel oil (common ingredients in processed foods)
  • Poultry with the skin on
  • Processed meats like sausage, hot dogs, and salami
  • Some baked and fried foods including ingredients like lard and butter

Replace high-fat foods with lean options, such as those that are baked, steamed, or broiled instead of breaded, fried, or battered. 

Some examples of lean (low-fat) foods to eat while on Orlistat include:

  • Lean proteins like skinless poultry, lean red meat, white-fleshed fish, and eggs
  • Beans and lentils
  • Low-fat dairy products
  • Whole grains
  • Fruits
  • Vegetables

Temporarily reduce your fiber intake 

You’re more likely to experience issues with fecal incontinence during the first week or so of starting Orlistat. 

If you’re having a hard time making it to the restroom in time to have a bowel movement, you might need to cut back on your fiber intake (temporarily) until your body adjusts. 

Reducing your fiber intake can slow your digestive tract, which can lessen bowel urgency.

Remember that this change should only be made if needed and temporarily. After all, fiber is a beneficial nutrient found in healthy foods like whole grains, fruits, and vegetables, and avoiding those foods long-term isn’t recommended – especially if you’re wanting to lose weight!

Spread your fat intake evenly throughout meals

You can help reduce Orlistat side effects by spreading your fat intake throughout the day instead of eating a very high-fat meal all at once. 

The more moderate your fat intake, the less likely you are to have adverse side effects from fat malabsorption.

Who should not take Orlistat?

Orlistat might not be the best option for certain people. Examples of people/health conditions  where Orlistat might be contraindicated are below (but always check with your healthcare provider):

  • Abnormal absorption of food nutrients in the gastrointestinal tract (malabsorption)
  • Abnormal liver function tests
  • Anorexia nervosa or bulimia (eating disorders)
  • Blockage of normal bile flow (bile helps break down fats)
  • Calcium oxalate kidney stones
  • Decreased kidney function
  • High levels of oxalic acid in your urine
  • Kidney problems
  • Liver problems
  • People under the age of 18 years old
  • Pregnant or nursing women
  • Thyroid problems

Orlistat might interact with certain medications as well. Some of the medications Orlistat can interact with include:

  • Warfarin
  • Amiodarone
  • Ciclosporin
  • Thyroxine 

If you’re taking any other prescription medications, you should check with your healthcare provider and/or pharmacist to ensure it’s compatible with Orlistat.

In addition, Orlistat might cause deficiencies in fat-soluble vitamins (vitamins A, D, E, and K). These vitamins require the presence of fat to be absorbed, unlike the rest of the vitamins (like vitamin C, B vitamins, etc).

If you haven’t lost at least 5% of your body weight while taking Orlistat after three months of taking it, you should discontinue using it since it isn’t likely to be effective. It isn’t recommended to take Orlistat longer than six months, either.

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Are there any side effects of stopping Orlistat?

The main side effect of stopping Orlistat would be the reduction and resolution of any side effects you were experiencing. 

Your bowel movements will return to a more “normal” state (not greasy/oily), and you should regain better bowel control if you were experiencing fecal incontinence.

If you’d lost weight on Orlistat, you might notice weight gain after stopping it. Weight gain after stopping weight loss medications is especially common if you didn’t make any lifestyle changes while you were taking the medication. 

That doesn’t mean you’re guaranteed to gain weight once stopping Orlistat – but you are more likely to experience weight regain if you were solely relying on Orlistat for losing weight.

How does Orlistat work?

Orlistat is a lipase inhibitor, which means it stops your body from breaking down and absorbing fats. Lipase is an enzyme that specifically breaks down dietary fats. 

Without the action of lipase, fats aren’t broken down into fatty acids, which are the form that your body can absorb.

So what happens to the fat that isn’t absorbed by your stomach and intestines? It’s excreted in your stool (feces), which means you didn’t absorb the calories from the fat.

What is the dosing schedule for Orlistat?

The typical dosing schedules are as follows:

  • Alli (over-the-counter/non-prescription strength): 60 milligrams by mouth three times a day with each main meal containing fat.
  • Xenical (prescription-strength): 120 milligrams orally 3 times a day with each main meal containing fat.

How effective is Orlistat? 

According to a study, participants taking 120 milligrams (Xenical dosage) three times daily with meals lost an average of nearly 10% of their starting body weight (over 24 weeks). 

Participants in that study tolerated Orlistat well, though they experienced more side effects compared to the placebo group, which is expected.


Orlistat helps promote weight loss by blocking the action of lipase, an enzyme that breaks down fat.

Common side effects of Orlistat are increased fat excretion in your stool, such as oily stool, bowel urgency, and others.

To help reduce the side effects of Orlistat, take it as prescribed and cut back on your fat intake.

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  1. Filippatos TD, Derdemezis CS, Gazi IF, Nakou ES, Mikhailidis DP, Elisaf MS. Orlistat-associated adverse effects and drug interactions: a critical review. Drug Saf. 2008.
  2. Van Gaal LF, Broom JI, Enzi G, Toplak H. Efficacy and tolerability of orlistat in the treatment of obesity: a 6-month dose-ranging study. Orlistat Dose-Ranging Study Group. Eur J Clin Pharmacol. 1998.

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