In a small, 22-week study, researchers found that 16 overweight men and women lost an average of 17 pounds. They took the green (unroasted) coffee beans in supplement form and, for comparison, took a placebo at a different point of the study.
They did not change their diet. They were physically active. They lost more while on the supplements than while on placebo. They lost the most when on the higher of two coffee bean doses.
"We don't think it's the caffeine in it," says Joe Vinson, PhD, professor of chemistry at the University of Scranton.
He presented the findings Tuesday at the annual meeting of the American Chemical Society in San Diego. The results echo those of earlier studies, but Vinson used a larger dose of the green coffee beans.
The study included people 22 to 46 years old. It was funded by Applied Food Sciences, which makes the green coffee antioxidant supplement.
The results are interesting, but the study was small and short, so further study is needed, says Connie Diekman, RD, director of university nutrition at Washington University in St. Louis. She reviewed the findings for WebMD.
Green Coffee Beans for Weight Loss: Study Details
Vinson and his colleagues gave the men and women in the study a 700-milligram (mg) dose of the ground coffee beans and a 1,050 mg dose. They also gave them a placebo or inactive dose during the 22-week study.
The men and women cycled through each phase for six weeks. In between, they had ''wash-out'' periods where they didn't take any supplement. In this way, they served as their own comparison group.
"Their calories were monitored," Vinson says. They were not put on diets. Calorie intakes stayed about the same during the study. They averaged about 2,400 calories a day -- by no means a weight reduction plan.
They burned, on average, about 400 calories a day in physical activity, Vinson says. The study was done in India.
The 17-pound loss was the average. Some lost only about 7 pounds; others about 26 pounds.
Overall, body weight declined by an average of 10.5%. Body fat declined by 16%.
The study participants lost slightly more weight with the higher dose compared to the lower dose, but not a significant amount with the placebo, Vinson says. Vinson can't say for sure why the coffee bean extract seems to help weight loss. He suspects one explanation is the unroasted beans' chlorogenic acid.
Chlorogenic acid is a plant compound. It may have ''some effect on keeping down glucose absorption," which in turn helps reduce weight, Vinson says.
Once coffee beans are roasted, the chlorogenic acid breaks down.
None of the people in the study reported side effects, Vinson says. The capsules are extremely bitter, he says. They are best taken with a lot of water before a meal, he says.
A larger study of about 60 people is planned, Vinson says.
These findings were presented at a medical conference. They should be considered preliminary, as they have not yet undergone the "peer review" process, in which outside experts scrutinize the data prior to publication in a medical journal.