What is Orlistat? Weight Loss, Forms & Side Effects

If you’ve been asking yourself, ‘What is Orlistat’, you’ve come to the right place. Orlistat is a medication that aids weight loss by preventing the body from absorbing some of the fat from food. Available in both prescription orlistat (Xenical) and over the counter (Alli), it works by inhibiting fat-digesting enzymes in the digestive system. By reducing fat absorption, taking orlistat helps certain individuals lose weight when combined with a calorie-controlled diet and regular exercise. However, it can also cause digestive changes, such as increased bowel movements, and may affect the absorption of fat-soluble vitamins.

If you are considering taking orlistat, it is important to understand its benefits, side effects, and how it fits into a comprehensive weight management plan. This guide provides an in-depth look at how orlistat works, how to take it, potential side effects, and its role in achieving a healthy weight.

Key Takeaways

• Orlistat is a lipase inhibitor that helps compatible overweight adults lose weight by blocking dietary fat absorption.
• It is available in prescription orlistat (Xenical) and an over-the-counter version (Alli).
• Side effects of orlistat, include changes in bowel movements, fat-soluble vitamin deficiencies, and potential kidney stones.

Understanding Orlistat

Orlistat is a weight management medication classified as a lipase inhibitor. It is primarily used to assist individuals in losing weight by blocking the digestion and absorption of dietary fat. Unlike appetite suppressants, which work on the central nervous system, orlistat works directly in the digestive system, making it a unique approach to weight reduction.

This medication is commonly prescribed to overweight adults with a body mass index (BMI) of 30 or higher. However, it is also approved for those with a BMI of 27 or higher who have additional health risks such as high blood pressure, type 2 diabetes, or high cholesterol. The goal of taking orlistat is to help individuals achieve and maintain a healthy weight, reducing the risks of obesity-related conditions.

Orlistat is not a standalone solution—for optimal effectiveness, it must be combined with a reduced-calorie, low-fat diet and regular physical activity. To reduce fat intake, choose low-fat dairy options and lean cuts of meat when using orlistat. It is designed for long-term use under the guidance of a health care provider, and studies suggest that individuals who adhere to taking orlistat as prescribed tend to experience more significant weight loss results than those relying solely on lifestyle changes.

“Orlistat works by inhibiting enzymes in the digestive system that break down fat, leading to less absorption of calories from fat,” explains Matthew Olesiak, MD, Chief Medical Director of SANE MD. “When combined with diet and exercise, it can be an effective tool for weight management.”

Comparison of Prescription Orlistat (Xenical) and Over-the-Counter Orlistat (Alli)

Feature	Prescription Orlistat (Xenical)	Over-the-Counter Orlistat (Alli)
Dosage	120 mg per capsule	60 mg per capsule
Availability	Pharmacies with prescription	Available in stores & online
Intended Users	BMI ≥ 30 or BMI ≥ 27 with health risks	BMI ≥ 25 seeking weight loss support
Prescription Required	Yes	No
Insurance Coverage	May be covered	Not covered
Primary Use	Medically supervised weight management	General weight loss aid
Common Side Effects	Oily stools, increased bowel movements, nutrient deficiencies	Mild digestive discomfort, occasional bowel urgency

How Orlistat Works for Weight Loss

Orlistat’s primary function is to block dietary fats from being absorbed in the small intestine. Normally, the body breaks down dietary fat using lipase, an enzyme that helps digest and process fat for energy. Orlistat works by inhibiting this enzyme, preventing approximately 25–30% of dietary fat from being absorbed. The undigested fat is then excreted through bowel movements rather than stored in the body as excess weight.

Because orlistat reduces the absorption of dietary fats, it also impacts calorie intake, leading to gradual weight loss over time. However, it is important to note that taking orlistat does not mean an individual can consume unlimited fat. In fact, excessive fat intake while using orlistat can lead to uncomfortable gastrointestinal effects such as oily stools, diarrhea, and increased urgency for bowel movements.

Several clinical studies have confirmed the effectiveness of orlistat for weight reduction. Research shows that individuals who take orlistat in combination with a low-fat and reduced-calorie diet lose more weight than those following diet and exercise alone. On average, people using orlistat can lose 5–10% of their initial body weight over six months.

However, orlistat is not a miracle solution. For sustained weight management, it must be used alongside a calorie-controlled diet and regular physical activity. Long-term success also depends on maintaining a healthy weight and making lifestyle adjustments beyond the duration of taking orlistat.

Forms of Orlistat

Orlistat is available in two primary forms: prescription (Xenical) and over-the-counter (Alli). Both versions block dietary fat absorption in the same way, but they differ in dosage, accessibility, and intended use.

Prescription Orlistat (Xenical)

Xenical is the prescription-strength form of orlistat, containing 120 mg per capsule. The normal prescribed dose of Xenical is one 120 mg capsule taken three times a day with each meal. It is typically prescribed by a health care provider for individuals with a body mass index (BMI) of 30 or higher, or those with a BMI of 27 or higher who have obesity-related conditions such as high blood pressure, thyroid disease, or type 2 diabetes.

Because prescription orlistat is more potent, it is often used under medical supervision to ensure safe and effective weight management. Prescribing orlistat is common in cases where lifestyle modifications alone have not resulted in sufficient weight loss. Patients taking Xenical are advised to adhere to a calorie-controlled diet with low fat intake to minimize side effects of orlistat, such as oily stools and increased bowel movements.

Insurance may cover this version of orlistat when prescribed for obesity management, but coverage varies depending on the provider and specific patient conditions.

Over the Counter Version (Alli)

Alli orlistat is the over-the-counter version of orlistat. It contains 60 mg per capsule, which is half the strength of prescription orlistat. It is available without a prescription and is marketed for overweight adults who want to lose weight through a combination of diet and exercise. The recommended dosage of Alli for weight loss is one 60 mg capsule taken with a fat-containing meal up to three times a day.

Although Alli is less potent than Xenical, it still effectively blocks dietary fat absorption and can help individuals achieve modest weight loss when taken with a low fat diet. It is recommended for individuals with a BMI of 25 or higher who want to enhance their weight loss efforts without requiring a prescription.

Since taking orlistat at any dose can cause changes in bowel movements, those using Alli orlistat should also follow a low-fat diet to avoid unpleasant digestive side effects. Users may also need to take a multivitamin supplement to ensure they receive enough fat-soluble vitamins (A, D, E, and K) since orlistat reduces the absorption of these nutrients.

Alli is not typically covered by insurance, as it is considered an over-the-counter weight management aid. However, its accessibility and lower cost make it a popular option for individuals seeking additional support in losing weight.

Which Form of Orlistat is Right for You?

The choice between prescription orlistat (Xenical) and over the counter Alli orlistat depends on an individual’s weight loss goals, medical history, and health care provider recommendations. Alli is a 60-milligram, over-the-counter version of orlistat, whereas Xenical is a 120-milligram prescription drug. Xenical is better suited for individuals with higher BMI levels or weight-related health conditions requiring medical supervision.

In contrast, Alli may be a good option for overweight people who do not qualify for prescription treatment. Regardless of the version used, taking orlistat should always be combined with a reduced-calorie diet and regular physical activity for the best results.

How to Take Orlistat

To maximize the effectiveness of orlistat, it should be taken with each fat-containing meal, up to three times per day. Orlistat Xenical is taken as a 120 mg capsule up to three times a day with each main meal. The medication works by targeting dietary fat within the digestive system, so if a meal does not contain fat, taking orlistat is unnecessary.

Should you choose Orlistat, you’ll need to follow a few dietary principles to prevent troublesome or embarrassing side effects.

For best results, orlistat should be paired with a low-calorie-low fat diet that contains no more than 30% of daily calories from fat. You should evenly divide the amount of daily fat, carbohydrates, and protein over three main meals while taking orlistat. This helps reduce the likelihood of gastrointestinal side effects such as oily stools and increased bowel movements. If a meal is particularly high in fat, taking orlistat may cause more pronounced side effects.

To minimize nutrient deficiencies, individuals should take a multivitamin supplement containing fat-soluble vitamins (A, D, E, and K) and beta carotene at least two hours before or after taking orlistat. They should also avoid added fat or oil when cooking and prefer methods like grilling, poaching, or baking while on orlistat. Because orlistat blocks fat absorption, it can also hinder the absorption of these essential nutrients, making supplementation necessary.

“It’s important to monitor your fat intake, as excessive fat intake can lead to more intense side effects of orlistat,” says Dr. Olesiak.

If a dose is missed, it should not be taken later or doubled—instead, the user should continue with the next meal as scheduled. Patients taking orlistat should inform their healthcare provider about all other medications, vitamins, and supplements they are using to assess interaction risks. Individuals should follow their health care provider’s recommendations to avoid potential interactions with other medicines.

Side Effects of Orlistat

While orlistat effectively aids weight loss, its mechanism of action may cause side effects, especially within the digestive system. Since orlistat blocks the breakdown of dietary fats, the unabsorbed fat is excreted through bowel movements, leading to noticeable changes in digestion.

Common gastrointestinal side effects include:

• Changes in bowel movements, including frequent, loose, or oily stools
• Increased urgency to defecate, sometimes leading to difficulty controlling bowel movements
• Flatulence with discharge, resulting from excess unabsorbed fat in the intestines

Due to excessive fat intake, individuals who consume a high-fat meal while taking orlistat may experience more pronounced side effects. See our Orlistat diet guide to learn what to eat and what to avoid while taking this medication.

Other potential side effects include:

• Gallbladder problems, such as pain in the upper right abdomen, nausea, or discomfort
• Kidney stones, which can develop from increased oxalate levels in the urine
• Liver injury, though rare, has been reported in some users; symptoms include jaundice, fatigue, or dark urine

Less common but serious adverse effects may include allergic reactions, such as rash, swelling, or difficulty breathing. Individuals experiencing severe liver injury symptoms or signs of an allergic reaction should stop taking orlistat immediately and consult a health care provider. If you experience signs of liver injury, such as nausea and yellow skin, contact your doctor immediately.

Despite these risks, orlistat reduces the amount of fat absorbed and has been proven effective in helping overweight adults achieve and maintain a healthy weight when used properly.

Precautions and Drug Interactions

Individuals with malabsorption syndrome, organ transplant history, or problems absorbing food should avoid taking orlistat. Pregnant and breastfeeding individuals should also not use orlistat, as it can pass into breast milk.

Orlistat blocks fat absorption, which can interfere with the effectiveness of other medications, including cyclosporine, levothyroxine, and some treatments for epilepsy. Therefore, caution and possible dose adjustments are required. If orlistat is taken with cyclosporine, it should be taken at least three hours before or after orlistat.

If taking levothyroxine, it should be taken four hours before or after using orlistat.

If a missed dose occurs, users should not take a double dose but instead continue with the next meal as usual.

Does Orlistat Help You Lose More Weight?

Studies indicate that individuals who take orlistat alongside a low-fat diet and exercise tend to lose more weight than those relying on lifestyle changes alone. The goal is to achieve a 5% weight loss within three months of starting orlistat. However, sustainable weight management still requires long-term commitment to a reduced calorie diet and regular physical activity.

By limiting fat intake and enhancing weight reduction efforts, orlistat reduces the risk of obesity-related conditions like high blood pressure and weight gain. However, adherence to taking orlistat as directed and consulting a health care professional are key to achieving and maintaining a healthy weight.

Frequently Asked Questions About Orlistat

Orlistat is a widely used weight loss medication that helps compatible individuals manage their body weight by reducing dietary fat absorption. Since weight loss drugs vary in how they work and their effectiveness, many people have questions about how orlistat works, its side effects, and how it compares to other treatments like Ozempic.

Below are answers to some of the most frequently asked questions about taking orlistat.

1. Is orlistat a good weight loss drug?

Yes, orlistat is considered an effective weight loss medication, especially when combined with a reduced calorie diet and regular physical activity. Clinical studies show that individuals who take orlistat can lose more weight than those following diet and exercise alone. It works by blocking about 25–30% of dietary fat from being absorbed, which can help individuals achieve gradual and sustained weight loss.

However, taking orlistat requires a commitment to a low-fat diet, as high-fat meals can cause digestive discomfort.

2. Is orlistat like Ozempic?

No, orlistat and Ozempic are different types of weight loss medications that work in distinct ways. Orlistat is a lipase inhibitor, which prevents the body from absorbing dietary fats, while Ozempic (semaglutide) is a GLP-1 receptor agonist that helps regulate blood sugar and appetite.

Unlike orlistat, which works in the digestive system, Ozempic affects insulin levels and the brain’s appetite control center. Both can aid in weight loss, but Ozempic is primarily prescribed for managing type 2 diabetes, whereas orlistat is used specifically for weight loss.

3. What is the strongest weight loss pill?

There is no single “strongest” weight loss pill, as effectiveness depends on individual health conditions and treatment goals. However, orlistat is one of the most widely used and FDA-approved options. Comparing orlistat and phentermine for weight loss can help determine which medication may be more suitable based on individual needs. Other prescription medications, such as phentermine-topiramate (Qsymia) and liraglutide (Saxenda), may lead to more significant weight loss results but often work differently than orlistat. Ozempic and Wegovy (semaglutide) have gained attention for their appetite-suppressing effects and potential for significant weight loss.

The best medication depends on a person’s medical history, health care provider recommendations, and personal response to treatment.

4. Does orlistat have side effects?

Yes, taking orlistat can cause side effects, mainly related to digestion. Since orlistat blocks the absorption of dietary fats, the unabsorbed fat is eliminated through bowel movements, leading to symptoms like oily stools, increased urgency, and flatulence. Some individuals may also experience gallbladder problems, kidney stones, or mild liver injury.

Additionally, orlistat reduces the absorption of fat-soluble vitamins, so users should take a multivitamin supplement containing beta carotene and vitamins A, D, E, and K. While most side effects of orlistat are mild, severe reactions should be reported to a health care provider.

5. What is the major side effect of using orlistat?

The most common and significant side effect of orlistat is gastrointestinal discomfort, particularly changes in bowel movements. Since orlistat blocks fat digestion, unabsorbed fat is excreted, leading to oily stools, diarrhea, and an urgent need to use the bathroom. These symptoms are usually mild and occur more frequently when consuming a high-fat meal.

To minimize discomfort, individuals should follow a low-fat diet while taking orlistat. In rare cases, orlistat has been linked to kidney stones, gallbladder problems, and liver injury, making it important to consult a health care provider if unusual symptoms arise.

Conclusion

Orlistat is a well-established weight loss medication that works by blocking dietary fat absorption, helping individuals lose weight when combined with a calorie-controlled diet and regular exercise. Available in both prescription orlistat (Xenical) and an over-the-counter version (Alli), it provides a non-stimulant approach to weight management. While orlistat works effectively in promoting gradual weight loss, it also comes with potential side effects, particularly digestive changes related to bowel movements.

For those considering taking orlistat, it is crucial to follow a low fat diet, take a multivitamin supplement to counteract possible nutrient deficiencies, and consult a health care provider for guidance. Though orlistat reduces fat intake and can aid in achieving a healthy weight, long-term success depends on sustained lifestyle changes, including proper diet and exercise. By understanding how to take orlistat correctly and managing expectations, individuals can use it as an effective tool in their weight management journey.