FLEX has long recommended synephrine, the extract from bitter orange (Citrus aurantium) for fat loss. A recent study confirms that this supplement can aid fat loss and is very safe. It’s especially effective when taken with the other citrus extracts naringin and hesperidin. The graph shows the increase in resting metabolic rate as compared to a placebo when subjects consumed synephrine alone, synephrine plus naringin, or synephrine plus naringin and hesperidin. None of the supplements changed heart rate or blood pressure, supporting their safety.