Alli weight-loss pill: Does it work?

Is Alli — an over-the-counter weight-loss pill — the solution to your weight-loss woes?

By Mayo Clinic Staff

Alli (pronounced AL-eye) is an over-the-counter drug meant for overweight adults struggling to shed excess pounds. With its easy access and weight-loss promises, is Alli your answer for losing weight?

What is Alli?

Alli is a 60-milligram, over-the-counter version of orlistat (Xenical), a 120-milligram prescription drug. Both Alli and Xenical are meant to be used as part of a weight-loss plan, along with a low-calorie, low-fat diet and regular physical activity.

Alli is approved by the U.S. Food and Drug Administration for use in adults 18 and older who have a body mass index (BMI) of 25 or more. Xenical is approved for use in adults with a BMI of 30 or more (obese). Xenical is also approved for those with a BMI of 27 to 30 (overweight) who have other health risk factors such as high blood pressure or diabetes.

Are there concerns about orlistat?

The FDA published a safety review of orlistat in 2010 because of rare reports of serious liver injury in people using it. The FDA found no evidence to confirm that orlistat was the cause of the reported liver injuries.

However, Alli and Xenical labels were revised because of the reports. Talk to your health care provider right away if you have signs or symptoms of liver injury, such as:

  • Itching
  • Loss of appetite
  • Yellow eyes or skin
  • Light-colored stool
  • Brown urine

How does Alli work?

Orlistat (the active ingredient in Alli) promotes weight loss by decreasing the amount of dietary fat absorbed in your intestines.

Lipase, an enzyme found in the digestive tract, helps break down dietary fat into smaller parts, so it can be used or stored for energy. Orlistat blocks the work of lipase. When you take the drug with a meal, about 25% of the fat you eat isn't broken down. The fat is passed through bowel movements.

How much weight could I lose using Alli?

Alli may help you lose weight. But the weight loss will likely be modest. For example, it may be just a few pounds more than you would lose with diet and exercise alone.

In some studies, more than 40% of people taking Alli while following a calorie-restricted diet and increasing physical activity lost 5% or more of their body weight within a year. Clinically meaningful weight loss, generally defined as 5% or more of body weight, means that there is enough weight loss to begin lowering the risk of heart disease, diabetes and other diseases.

People who ate a calorie-restricted diet, exercised regularly and took Alli lost an average of 5.7 pounds (2.6 kilograms) more in one year than did people who only dieted and exercised.

How is Alli taken?

You take one 60-milligram Alli pill within an hour of a fat-containing meal up to three times a day. You should spread your daily fat intake over the three main meals. Fat intake should be no more than 30% of total calories. The manufacturer recommends a fat intake of about 15 grams a meal.

If you eat a meal that has no fat, then you don't need a dose of Alli. If you take Alli with a high-fat meal, you'll likely experience more-severe digestive side effects.

Alli can reduce the absorption of fat-soluble nutrients, including beta carotene and vitamins A, D, E and K. Take a multivitamin at least two hours after your last dose of Alli. For some people, this timing works out best to be at bedtime.

Does Alli have side effects?

The active ingredient in Alli, orlistat, causes digestive side effects related to undigested fats passing through your digestive system. They generally lessen over time and with proper use of the drug. These side effects include:

  • Stomach pain or upset stomach
  • Oily discharge from the anus
  • Gas with oily anal discharge
  • Oily stools
  • More-frequent bowel movements
  • Urgent or hard-to-control bowel movements

Other possible side effects include:

  • Headache
  • Back pain
  • Common cold symptoms
  • Menstrual changes

When shouldn't you take Alli?

Before taking Alli, talk with your health care provider about possible interactions with other drugs, particularly if you take drugs for any of the following conditions:

  • Diabetes
  • Thyroid disease
  • Irregular heartbeat
  • Heart disease
  • Seizures
  • HIV

It's also important to check with your health care provider if you've had:

  • Gallbladder problems
  • Kidney stones
  • Pancreatitis
  • Irritable bowel syndrome

Alli isn't recommended if you:

  • Are at a healthy weight
  • Have had an organ transplant
  • Are taking cyclosporine (Neoral, Sandimmune, others)
  • Have problems already absorbing food
  • Are pregnant or breastfeeding

How long do I need to take Alli?

A weight-loss plan with diet, exercise and drug therapy is generally considered successful if you lose about 1 pound (0.5 kilogram) a week during the first month. Losing 5% or more of the pre-treatment body weight within one year is also considered successful.

If the treatment is successful, you are more likely to keep weight off or lose more weight if you continue with the diet, exercise and drug treatment plan.

Most weight loss with the drug occurs within the first few months. If you have followed the diet and exercise plan and have not lost at least 5% of your initial body weight within a few months, continuing the drug may be of little benefit.

If you haven't lost 5% of your body weight within a year on the plan, stopping the drug would be a reasonable choice. The risks, side effects and cost related to taking the drug likely override any potential benefit.

How does Alli fit into a healthy weight-loss plan?

Alli isn't an easy answer to weight loss. Losing weight and keeping it off require a commitment to eat a healthy, calorie-controlled diet and get regular physical activity.

Work with your health care provider to evaluate the potential benefits and risks of Alli or any other weight-loss drugs. As a team, you and your provider can create the right weight-loss plan for you.

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March 12, 2022 See more In-depth