Prescription Weight-loss Medicines

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Do prescription weight-loss medicines really work?

When combined with a reduced-calorie diet and regular physical activity, prescription weight-loss medicines can help obese people lose weight. People who use these drugs may not feel as hungry, or they may feel full after eating only a small amount of food.

What types of prescription weight-loss medicines are available?

Prescription weight-loss medicines include diethylpropion, benzphetamine, phendimetrazine, phentermine, mazindol, and orlistat. Orlistat works by keeping your body from digesting some of the fat that you eat. The other types of weight-loss medicines listed are believed to work by reducing appetite.

Although some weight-loss supplements containing ephedra, ephedrine or caffeine are available without a prescription, it is not known whether these drugs are safe. Such supplements have been linked to reports of heart attack, seizure, stroke and death. It is important to talk to your doctor if you are considering taking a weight-loss supplement or if you are already taking one.

Are prescription weight-loss medicines used for people who are just slightly overweight?

No. Prescription weight-loss medicines are only for people who are very obese. Most of these medicines are designed for people who weigh 20% or more above what is ideal for their height and body type or who have a high body mass index (BMI). The BMI is a measure of your weight and height. Your doctor can tell you if prescription weight-loss medicines might be helpful for you.

Are there any side effects from using prescription weight-loss medicines?

Yes, there are possible side effects associated with prescription weight-loss medicines. Common side effects may include the following:

  • Nervousness
  • Irritability
  • Headaches
  • Dry mouth
  • Nausea
  • Constipation
  • Abdominal pain
  • Diarrhea
  • Sleep problems (such as insomnia and very intense dreams)

Orlistat may cause gas, frequent or uncontrollable bowel movements, diarrhea and oily stools. A lower strength dose of over-the-counter orlistat also is available. In May 2010, the U.S. Food and Drug Administration issued a new warning about the use of prescription or over-the-counter orlistat. In rare cases, orlistat may cause serious liver injury. Call your doctor immediately if you take orlistat and notice any of the following symptoms of liver injury:

  • Itching skin
  • Yellow eyes or skin
  • Urine that is brown or dark-colored
  • Pale-colored stool
  • Loss of appetite
  • Abdominal pain

Sometimes other weight-loss medicines also can have serious side effects, such as high blood pressure. Your family doctor can tell you more about these side effects.

How can I avoid gaining weight back when I stop using the medicine?

There is no easy cure for being overweight. Prescription weight-loss medicines can help you get off to a good start, but once you stop taking them, the weight you lost may come back. To keep the weight off, you must eat a healthy diet and be physically active on a regular basis. You must continue these healthy habits even after you stop taking the medicine. Remember that losing weight and keeping it off is a lifelong effort.

Do I have to use prescription weight-loss medicines to lose weight?

No. If you decide weight-loss medicines aren't right for you, you can still meet your weight-loss goals. It's important to develop healthy eating habits, but don't expect to change everything overnight. Start by training yourself to eat without doing anything else at the same time. For example, don't eat while you watch TV. Focus on what you're eating. Try to eat slowly.

Next, change what and how much you eat. Your doctor can help you create a low-calorie diet plan that will help you lose weight.

It is also important to be physically active. A good goal for many people is to work up to exercising for at least 30 minutes, 4 to 6 times a week. Regular exercise helps you burn calories faster, even when you are sitting still. Exercise also helps you burn fat and build muscle.

Aerobic exercise raises your heart rate and helps you burn calories. Aerobic exercises include swimming, brisk walking, jogging and bicycling. Anaerobic exercise, such as weight training, is also good because it adds muscle mass to your body. Muscle burns calories faster than fat.

Be sure to check with your family doctor before you begin an exercise program. He or she can help you create an exercise plan that will help you meet your goals.

Written by familydoctor.org editorial staff

Reviewed/Updated: 05/14
Created: 04/99

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