Alli Weight-Loss Pill: Does It Work?

Is Alli the solution to your weight-loss woes? A Mayo Clinic specialist discusses the effectiveness of Alli, an over-the-counter weight-loss pill.

Another drug is available to aid your weight-loss efforts, but this time you don't need a prescription. Alli (pronounced AL-eye) is meant for overweight adults who are struggling to shed excess pounds. With its easy access and weight-loss promises, is Alli your answer to losing weight permanently?

Here, Donald Hensrud, M.D., a preventive medicine and nutrition specialist at Mayo Clinic, Rochester, Minn., answers common questions about Alli.

What is Alli?

Alli is the reduced-strength version of orlistat (Xenical), a prescription drug to treat obesity. It's approved for over-the-counter sale to overweight adults 18 years and older. Alli is meant to be used in conjunction with a low-calorie, low-fat diet and regular exercise.

How does Alli work?

Alli promotes weight loss by decreasing absorption of fat by the intestines, which reduces the number of calories you absorb.

Lipase, an enzyme found in the digestive tract, helps break down dietary fat into smaller components, so it can be used or stored for energy. Alli works by disabling lipase, which prevents the enzyme from breaking down the fat while it's in your digestive tract. The undigested fat continues through the intestines and is eliminated through bowel movements.

Alli is taken with fat-containing meals, up to three times a day. Because of how Alli works, it's recommended that you eat no more than 15 grams of fat with each meal. Eating higher amounts of fat can cause unwanted effects, such as urgent bowel movements, diarrhea and gas with oily spotting.

How much weight could I lose using Alli?

Alli can help you lose weight, but the weight loss likely won't be great — perhaps just a few pounds more than you would lose with diet and exercise alone. Only a small number of studies have evaluated the effectiveness of Alli. And many of the weight-loss estimates are based on studies conducted on its prescription-strength counterpart, Xenical.

The average weight loss for prescription-strength Xenical is modest — about 6 pounds greater than diet and exercise alone after one year. So at half the strength, Alli could conceivably result in an average of 3 pounds lost in a year in addition to the approximately 8 pounds you could expect to lose from diet and exercise alone.

When shouldn't I take Alli?

You shouldn't take Alli if you:

Are at a healthy weight

Are taking cyclosporine

Have had an organ transplant

Have problems absorbing food

The drug also may pose risks for anyone who takes blood-thinning medication or has diabetes or thyroid disease.

Orlistat decreases the absorption of certain fat-soluble vitamins — for example, vitamins A, D and E. If you're taking Alli, you need to take a daily vitamin supplement (at a time different from when you take Alli) to prevent potential nutrient deficiencies.

How long do I need to take Alli?

According to the manufacturer, most weight loss occurs within the first six months. Many people who take medications to lose weight regain the weight they lost when they stop taking the medication. Therefore, to keep the weight off, many people continue taking medications indefinitely along with eating a low-calorie diet and exercising regularly.

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

As you consider Alli as a weight-loss aid, make sure that you make every effort to exercise, change your eating habits and adjust any other lifestyle factors that have contributed to your excess weight. Alli isn't the easy answer to weight loss and is meant only to supplement — not replace — a healthy diet and regular exercise.

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