Bitter orange extract comes from the Citrus aurantium fruit and contains synephrine, a compound similar to ephedrine. It is believed to suppress appetite and increase metabolism. To use, follow the recommended dosage on the product label. Synephrine works by stimulating the central nervous system, which may help increase calorie burning and reduce food intake. The effectiveness varies among users, with some reporting results within weeks. Side effects may include increased heart rate, high blood pressure, and potential interactions with certain medications.