Use of Prescription Weight Loss Pills by U.S. Adults in 1996–1998

Summaries for Patientsare a service provided by Annalsto help patients better understand the complicated and often mystifying language of modern medicine.

Summaries for Patients are presented for informational purposes only. These summaries are not a substitute for advice from your own medical provider. If you have questions about this material, or need medical advice about your own health or situation, please contact your physician.

The summary below is from the full report titled "Use of Prescription Weight Loss Pills among U.S. Adults in 1996–1998." It is in the 20 February 2001 issue of Annals of Internal Medicine(volume 134, pages 282-286). The authors are LK Khan, MK Serdula, BA Bowman, and DF Williamson.

What is the problem and what is known about it so far?

Several prescription weight loss drugs have been available in the United States. The Food and Drug Administration approved phentermine in 1959 and approved fenfluramine in 1973 for short-term use (a few weeks). In 1996, dexfenfluramine was approved for longer use (up to 1 year). In 1997, sibutramine was approved for short-term use. These four drugs work by limiting hunger. Orlistat, a drug that blocks the amount of fat absorbed from food, was approved in 1999 for up to 2 years of treatment. Fenfluramine or dexfenfluramine was often used in combination with phentermine; this combined weight loss treatment is known as "fen-phen." Reports of heart valve problems in "fen-phen" users led the manufacturer to stop selling fenfluramine and dexfenfluramine in the United States in September 1997. Little is known about how many people actually take these different drugs or how overweight these persons are when they start taking them.

Why did the researchers do this particular study?

To learn about who takes prescription weight loss drugs.

Who was studied?

139,779 adults who participated in a national telephone survey about health behaviors.

How was the study done?

State health departments conducted a telephone survey by using random-digit dialing to select a sample of adults. Among questions related to health behaviors, the survey asked whether participants had taken any physician-prescribed weight loss pills in the previous 2 years. It also asked participants who took diet pills about their height, present weight, and weight before using the pills.

What did the researchers find?

More than 2 of every 100 respondents (2.5%) had taken a prescription weight loss pill during the past 2 years. This means that approximately 4.6 million U.S. adults may have used prescription diet pills in 1996–1998. Reported use was highest among women, white respondents, and Hispanic respondents. Nearly half of persons who used weight loss pills were not overweight when they started taking the drugs.

What were the limitations of the study?

The survey did not collect information on the specific pills used; duration of treatment; drug dose; or medical conditions, such as heart disease or diabetes. Prescription weight loss drugs are recommended for people who are obese or those who are overweight and also have diabetes mellitus or heart disease; inappropriate drug use may therefore have been higher than this study suggests. These results might not reflect current use because different weight loss drugs are currently available.

What are the implications of the study?

About 1 in 40 adults in the United States used prescription weight loss pills in 1996–1998. Nearly half of the persons who used diet drugs were below the recommended minimum weight when they started taking the drugs.