Fat Burner #13: CITRUS AURANTIUM (bitter orange, synephrine)

What is it?

Citrus aurantium, commonly referred to as bitter orange, has been used for thousands of years in Traditional Chinese Medicine to improve overall health. That is, until recently, when science discovered compounds (the most well-known being synephrine) from these little orange fruits demonstrated equally powerful thermogenic ("fat-burning") activity. In fact, synephrine has prominently become referred to as ephedra's "calmer chemical cousin" because it increases the body's metabolic rate or ability to burn calories, without producing negative side effects on the central nervous system and the cardiovascular system.

How it works

Citrus aurantium appears to work by way of its active compound called synephrine, which is a bit like ephedra (an amphetamine-like chemical formerly found in a lot of weight-loss and performance products). Like ephedra, this chemical also appears to reduce appetite and boost metabolism—the rate our bodies burn calories—thus stimulating fat loss. Unlike ephedra, though, you're likely to experience very little, if any, side effects with Citrus aurantium. This is because Citrus aurantium contains chemicals called amines (tyramine and octopamine), which are not as lipophilic—meaning they do not cross the blood/brain barrier as easily as ephedra, which reduces central nervous stimulation and cardiovascular effects. In other words, this could mean no nervous energy (i.e., shakes or jitters), increased heart rate, or insomnia.

What does the science say?

According to recent research at McGill University, another reason Citrus aurantium gives you a smooth flow of energy without the jitters is because it stimulates certain receptors (called beta-3 adrenergic receptors) that help break down fat—known as lipolysis. Simultaneously, this stimulation causes an increase in the metabolic rate. Therefore, you burn fat without bothering other receptors (namely, beta-1, beta-2, or alpha-1) that over-stimulate your heart rate and blood pressure. In contrast, ephedra stimulates all alpha- and beta-adrenergic receptors, thus causing unwanted side effects. For this reason, synephrine is now being used as a replacement for central nervous stimulants like ephedra in many thermogenic formulas.

How to take it

Most leading research indicates that four to 20 mg of synephrine per day, which usually is provided by supplementing with 200 to 600 mg of a standardized Citrus aurantium extract (at three to six percent synephrine), may be most effective.