Before you consider whether to use any over-the-counter diet aid, find out if you really need to lose weight. A healthy weight is a weight that lowers your risk for health problems. For most people, body mass index (BMI) and waist size are good ways to tell if they are at a healthy weight.

If you practice healthy eating habits and are active enough to stay healthy, then weighing a few extra pounds is not bad for your health unless you have other medical problems. On the other hand, dieting can be bad for your health. Diets almost never work, and they can cause many people to fall into an unhealthy cycle of losing and gaining weight. This is often called yo-yo dieting. It may be harder on the body than just being overweight.

If you are thinking about losing weight, ask your doctor whether it's a good idea for you.

There are many products for weight loss that you can buy without a prescription at drugstores and supermarkets and over the Internet. Many of these have never been proved to work, and those that do work usually come with warnings.

What about Alli?

Alli (say "AL-eye") is a lower-dose version of the prescription drug orlistat (Xenical), which is used to treat obesity. You can buy Alli without a prescription.

Orlistat has been proved to help people lose weight.¹ It works by preventing fat absorption, so that the fat you eat moves through your intestines undigested. But the weight loss amounts to only a few pounds, and the drug's side effects can be very unpleasant.

The side effects include sudden loose stools and oily spotting on your underwear. The more fat you eat, the worse the side effects are, so it's best to limit fat while you are taking this drug.

Do not take Alli if you:

• Have had an organ transplant.
• Are pregnant or breast-feeding.

Talk to your doctor before you take Alli, but especially if you:

• Take blood-thinning medicines.
• Have diabetes or thyroid disease.

Most over-the-counter diet aids don't have to pass government tests for safety or effectiveness.

Long-term studies are the only way to tell if a medicine or supplement works and is safe. And there are very few such studies of diet aids. But we know about the following risks:

• Over-the-counter appetite suppressants shouldn't be used by people who have heart disease, high blood pressure, diabetes, kidney problems, thyroid problems, glaucoma, or depression.
• Appetite suppressants are only intended for use for a short time (8 to 12 weeks). But staying at a healthy weight is a lifelong effort. It is costly and possibly dangerous to depend on these medicines to control your weight for long periods of time. If you are going to use these drugs to help you lose weight, be sure to also make healthy changes to your diet and get regular exercise.
• Water-loss pills (diuretics, such as Aqua-Ban) only get rid of water and do not reduce the amount of fat in your body. Using water-loss pills to lose weight is not recommended and can be dangerous.
• Because diet supplements are not regulated, manufacturers sometimes make claims that aren't true. For example, just because the label says the supplement is "all natural" doesn't mean it's safe. Many things that are "natural" can still hurt you. And manufacturers may cite only their own studies to show how well their products work.
• Many products contain 20 or more ingredients, so it's really hard to know how all the ingredients will interact with each other in your body and how they will interact with any other medicines or supplements you are taking.
• You shouldn't take cough or cold medicines while you take some of these diet pills. They contain some of the same medicine, and you could get too much. Ask your pharmacist if it's safe to take cold medicine with the diet pills you are taking.

The U.S. Food and Drug Administration (FDA) warns people not to use certain diet aids that are known to be tainted with drugs or chemicals. You can find the FDA's warning list, which includes many popular diet aids, at www.fda.gov/ForConsumers/ConsumerUpdates/ucm103184.htm.

The FDA has banned the sale of ephedra (also known as ma huang) because of concerns about safety. The product has been linked to heart attacks, strokes, and some deaths. Ephedra and ephedrine—the active ingredient in ephedra—decrease appetite by increasing metabolic rate.

It's wise to talk to your doctor before you take any over-the-counter diet aid.

Your doctor is not likely to recommend that you use an over-the-counter diet aid in your efforts to reach a healthy weight and stay there. The best way to get to a healthy weight and stay there is to eat right and exercise regularly.

To be safe, always talk to your doctor before using any weight-loss product.