Green coffee beans are unroasted coffee beans. They contain high levels of chlorogenic acid, which is thought to have health benefits.
Early research suggests that taking green coffee extracts containing 50% to 70% chlorogenic acid can improve weight loss by about 5 kg (11 lbs) over 12 weeks. This is equivalent to a weight loss of about 0.5 kg (1 lb) per week.
Green coffeebean supplements are generally well tolerated and have few side effects. The most common side effect is mild gastrointestinal upset, such as diarrhea or constipation.
Overall, green coffee bean supplements appear to be safe and effective for weight loss in adults when taken at doses up to 700 mg per day for 12 weeks.