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Diet Pills and Weight Loss

Q: My 21-year-old son needs to lose weight. In addition to making lifestyle changes, he's interested in taking appetite suppressants. How do these medications work? Are any of them safe and FDA approved?

A: There are two types of FDA-approved weight-control medications: appetite suppressants and lipase inhibitors. Both are intended for those by adults at least 18 years old.

Appetite suppressants make a person less hungry by increasing the brain chemicals that affect his or her mood and appetite. Most of these prescription drugs are recommended for short-term use – no longer than 12 weeks, in large part because of the commonly experienced negative side effects: increased blood pressure and heart rate, sleeplessness, and nervousness.

There are several plant- and herb-based over-the-counter (OTC) appetite suppressants, such as hoodia gordonii. But they are not FDA approved, and little research is available about their effectiveness and side effects.

Lipase inhibitors are chemicals that reduce the amount of fat – and therefore the amount of calories – absorbed in the intestines. The drug Orlistat® is a lipase inhibitor commonly prescribed to treat obesity. A diluted version of it, called Alli®, became available as an OTC drug in 2007 and is FDA-approved for use by adults age 18 and over. The manufacturer suggests that it should be used for no longer than 6 months, and that it should be used along with a low-calorie/low-fat diet, exercise, and a daily multivitamin. Its side effects are similar to those for the stronger prescription version of Orlistat: gastrointestinal cramping, oily diarrhea, and unpredictable bowel habits. The FDA has since required warning labels on both of these drugs to help people be alert for signs of possible liver damage (yellow skin, brown urine, and others).

Research on appetite suppressants and lipase inhibitors shows that they can help people lose some weight. But the drugs were only studied when they were taken as part of a weight-loss program – one that included a reduced-calorie diet and exercise.

Remember the basics for losing weight: Calorie intake needs to be less than calorie expenditure. You can go to for specific nutritional information and to create a detailed calorie plan. You can also look into a credible weight loss support group such as Weight Watchers®.

Perhaps the most important thing you can do to help your son is encourage him to see a doctor, first to make sure that there are no underlying medical conditions that might be contributing to his weight gain. (Usually, weight gain relates to lifestyle behaviors such as diet and exercise habits.) Second, he can ask his doctor about weight loss pills and discuss the pros and cons. He'll likely find that a healthy diet and regular exercise are the keys to losing weight and keeping it off.

Visit the website of the NIH Weight-control Information Network for more information about the many drugs used to treat obesity.


1. National Institutes of Health. Weight-control Information Network. Prescription medications for the treatment of obesity.

2. Hoodia. Center for Complementary and Alternative Medicine.

Written by:: Don Hall, DrPH, CHES
Reviewed:: 5/7/2013

This information is provided for educational purposes only and is not intended to be a substitute for professional medical advice or diagnosis of specific medical conditions. You should seek prompt professional medical attention if you have a particular concern about your health or specific symptoms. Wellsource, Inc. is not liable for any health consequences resulting from your use of this site.