Green Coffee Bean by Natures Craft for Guaranteed Results or Your Money-back Scientifically Proven Results In 2012, the U.S. National Library of Medicine published a randomized, double blind, placebo-controlled study that evaluated the impact and safety of green coffee bean extract as a weight loss supplement. Over 12 weeks, participants lost an average of 17 pounds by taking GCA Green Coffee Bean Extract twice per day, making no other changes to their diet or exercise. On average, they lost 10% of their body weight and 16% of their total body fat. Moreover, they experienced no side effects of any kind. How Does It Work This product's weight loss effects are not caused by caffeine. Green Coffee Bean Extract only has approximately 20 mg of caffeine per serving, a cup of decaffeinated coffee. The key ingredient for weight loss is called chlorogenic acid.