Hydroxycitric acid (HCA), a derivative of citric acid, may improve weight loss results and reduce appetite. HCA inhibits ATP citrate lyase, a key enzyme for lipid metabolism. HCA also increases serotonin release, providing a reduction in appetite as well as improved mood.
A recent study found HCA to be safe and slightly effective for weight loss over placebo. Greater bioavailability was found when HCA was taken on an empty stomach. No side effects were found.