Appetite-suppressant drugs not panacea for obesity, experts warn

Focus efforts on behavioral modification in comprehensive programs

If your disease management program involves the use of the new appetite-suppressant drugs to treat obesity, beware. Although drugs such as dexfenfluramine (Redux) are becoming popular, their use is fraught with a major paradox: It is unclear whether use of the drugs is safe and effective after one year, even though that is when dieters need the drugs the most.

"There’s little justification for the short-term use of weight-loss drugs because most patients regain lost weight when they stop taking the medications," says Susan Yanovski, MD, director of the Obesity and Eating Disorders Program for the National Institute of Digestive Disorders and Kidney Diseases (NIDDK) in Bethesda, MD. "This does not mean that these drugs are ineffective but that obesity is a chronic disease that requires long-term treatment."

In fact, a task force established by NIDDK is so concerned about the use of appetite suppressant drugs that it recommends they be used only in "carefully selected patients." The National Task Force on the Prevention and Treatment of Obesity of the NIDDK recently reviewed published research over the last 30 years on weight loss and found only modest success with appetite-suppressant drugs, especially long term after six months.1

The task force found that single- and combination-drug therapy taken over six months or longer was only "moderately effective" for weight loss when compared with a placebo. Net weight loss attributable to weight-loss drugs ranged from 4.4 to 22 pounds, and most weight loss occurred during the first six months of treatment. After six months, weight was maintained or increased slightly, and most patients didn’t reach an "ideal" body weight. After 12 months, there were only a small number of patients studied, so the task force didn’t have enough information to determine the efficacy of the drugs for more than a year.

How long can drugs be used safely?

The task force says that to be effective, treatment of obesity with drugs may need to continue for years — perhaps for the lifetime of the patient. However, most of the medications are approved for short-term treatment only, with the exception of dexfenfluramine, which is approved for use up to 12 months. The makers of the newest appetite-suppressant drug, Redux, from Wyeth-Ayerst Laboratories in Philadelphia, are planning to perform a post-marketing, phase IV study of the drug to determine its safety and efficacy after one year, says company spokeswoman Audrey Ashby. But in the meantime, how long should Redux and other similar drugs be used?

"We just don’t know their long-term safety," says John P. Foreyt, PhD, director of the Behavioral Medicine Research Center at Baylor College of Medicine in Houston. "Here, we use them short term. Although it varies by individual patient, on average, patients stay on the drugs for four to six months."

He says after that time, a "plateau" occurs when weight loss isn’t as dramatic, but the patient usually has lost about 10% of his or her body weight.

"That’s a medically significant amount of weight," Foreyt notes.

However, in order to maintain weight loss, patients sometimes have to go off and on the drugs periodically, he adds. "But even that is pioneering territory," Foreyt says.

What is more important than drug therapy is making sure patients are involved in programs that include behavior modification. At Baylor, that includes having patients keep a diary to determine their food intake and exercise patterns.

"Then we help them design a program of getting up earlier for exercise and making gradual [reductions] in fat intake and looking at stress management," Foreyt says.

At the Baylor program, appetite-suppressant drugs are used "occasionally" in patients with "obesity that is interfering with their health."

"You can eat poorly and not exercise and take these drugs and lose weight, but the point is, you’re not going to be healthy," Foreyt explains. "The bottom line is still health, not weight."

There is controversy over how to identify which patients should receive drug therapy. The American Society of Bariatric Physicians (ASBP) in Englewood, CO, recommends that only to patients with a body-mass index (BMI) of 27 kg/m2, but they also say patients should have 30% body fat or more for women and 25% or more for men as minimum indications for treatment with the drugs.2 The BMI is determined by taking the patient’s weight in kilograms and dividing it by the patient’s square height in meters.

The Massachusetts Medical Society’s Committee on Nutrition in Boston recommends drug therapy in patients with "medically significant" obesity who have gained 13.5 kg or more since 18 years of age.3 Drug labeling for Redux recommends a minimum BMI of 30 kg/m2 for treatment of patients without obesity-related risk factors, or 27 kg/m2 in the presence of risk factors.4

"I think there are very clear guidelines that have been set up by the Food and Drug Administration, and I think they should be followed," say Xavier Pi-Sunyer, MD, director of the division of endocrinology at St. Luke’s Roosevelt Hospital in New York City. "When the drug was approved, the labeling gave [the] recommendation . . . that if you don’t have any associated conditions, you shouldn’t use the drug unless your BMI is 30 or above. And if you have associated conditions, [you can use the drug] if the BMI is 27 or above. I don’t think anybody below a BMI of 27 should be taking these drugs."

Another issue with appetite-suppressant drugs is the risk of primary pulmonary hypertension (PPH), a potentially fatal condition that occurs in one in every 22,000 to 44,000 patients treated with the drugs.5 James Merker, a spokesperson for ASBP, says PPH can be detected early if patients are being seen regularly by a physician because blood pressure and other vital signs are being monitored. In addition, physicians should warn patients of the signs of PPH such as shortness of breath, chest pain, syncope, or edema in the lower extremities.

"Normally, [PPH] doesn’t even appear until after 120 days of therapy," he says. "We still feel that the small risk associated with the use of [appetite-suppressant drugs] is still heavily outweighed by the dangers of obesity. The comorbidity factors associated with obesity such as diabetes and hypertension are much more of a risk factor to someone’s health than the small incidence of PPH."

Drugs shouldn’t be focus of program

No matter how the drugs are prescribed, make sure they are used as part of a comprehensive program that doesn’t just focus on drug therapy, says Pi-Sunyer.

"Drug therapy is not very good," he says. "The treatment program that just bases its treatment on drugs is going to fail. What you want to do is change your lifestyle. That’s the kingpin for having successful weight loss and maintenance that requires changes in nutrition and activity. If you have someone who is having difficulty, then you can add a drug. The point is you shouldn’t use the drug as the primary modality for care of patients. It doesn’t work."

PI-Sunyer says that if patients don’t have a weight loss of more than four pounds in four weeks, the drug should be discontinued "because it will not work in that patient," he adds.

Yanovski agrees that appetite-suppressant drugs shouldn’t be the mainstay of treatment of obesity, which she terms a "chronic disease."

"It’s not enough to hand a patient a prescription and a diet sheet," says Yanovski. "Medicine may make it easier to resist temptation, but the ability to make long-term changes in diet and exercise remains the key to permanent weight loss and improved health."

[Editor’s note: To obtain a free copy of a fact sheet from the NIDDK, "Prescription Medications for the Treatment of Obesity," contact: The Weight-control Information Network, 1 WIN Way, Bethesda, MD 20892-3665. Telephone: (800) 946-8098 or (301) 570-2177. Fax: (301) 570-2186. E-mail:]


1. National Task Force on the Prevention and Treatment of Obesity. Long-term pharmacotherapy in the management of obesity. JAMA 1996; 276:1,907-1,915.

2. The American Society of Bariatric Physicians. Anorectic Usage Guidelines. The American Society of Bariatric Physicians, Englewood, CO; October 17, 1996.

3. Committee on Nutrition. Massachusetts Medical Society white paper on obesity treatment using drug therapy. Boston: Massachusetts Medical Society; April 17, 1996.

4. Redux product labeling, 1996. Wyeth-Ayerst Laboratories, Philadelphia.

5. Abenhaim L, Moride Y, Brenot F, et al. Appetite-suppressant drugs and the risk of primary pulmonary hypertension. N Engl J Med 1996; 335:609-616.