Alethea Turner, D.O., reports:

Unlike magic beans that make you grow, green coffee beans may make you lose weight - and fast.

A new study suggests taking green coffee bean extract, which is sold as a supplement in the United States, could be a safe and effective way to drop some pounds.

"Based on our results, taking multiple capsules of green coffee extract a day - while eating a low fat, healthful diet and exercising regularly - appears to be a safe, effective, inexpensive way to lose weight," study author Joe Vinson, a chemist at the University of Scranton in Pennsylvania, said in a statement.

Researchers gave up to 1,050 milligrams of green coffee bean extract to 16 overweight adults in their 20s and monitored their diet, exercise regimen, weight, heart rate and blood pressure for 22 weeks. Without changing their diet or exercise, study subjects lost roughly 10.5 percent - an average of 17 pounds - in overall body weight. No harmful side effects were noted, according to the study presented today at the American Chemical Society national meeting in San Diego.

How green coffee bean extract contributes to weight loss is unclear. But Vinson theorizes a chemical in the unroasted bean called chlorogenic acid could be responsible. Other experts suspect the stimulant properties of caffeine could be the culprit.

"I'd be happier if the research included pure caffeine, in the same amount as is contained in the two doses of [green coffee bean extract]," said Keith Ayoob, a registered dietitian and associate professor at the Albert Einstein College of Medicine in New York. "Then you'd know if the effects are due solely to caffeine or to something else in the beans, or to some combination thereof."

Although green coffee bean extract may be of some benefit for people seeking weight loss, experts say the small study should be interpreted with caution.

"It's premature to recommend this approach," said Dr. David  Katz, director of Yale University's Prevention Research Center. "The effects, if real, are likely to be modest and we don't know if they last over time."

"It's a supplement, not a substitute," Katz added. "The emphasis will always need to be on overall diet and physical activity."

Dr. Turner is a family medicine resident at Scottsdale Health Care in Arizona.