Joe Vinson of the University of Scranton in Pennsylvania and colleagues said the study involved 16 overweight or obese people ages 22-26, who took capsules of the extract or capsules containing a placebo, an inactive powder, for a total of 22 weeks.
The low dose consisted of 700 milligrams of the coffee extract, and the high dose was 1,050 mg. This "cross-over" study cycled participants through the two doses and the placebo, each for six weeks. Such studies have advantages because each person serves as his or her own "control," improving the chances of getting an accurate result, Vinson explained.
"The study participants' calories, carbohydrates, fats and protein intake did not change during the study, nor did their exercise regimen change," Vinson said.
Participants lost an average of 17 pounds during the 22 weeks of the study -- an average of a 10.5 percent decrease in overall body weight and a 16 percent decrease in body fat.
"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," Vinson told the American Chemical Society symposium in San Diego.
Vinson said the green coffee beans' effects were likely due to chlorogenic acid, which is present in unroasted coffee beans.