Clayton's Health Facts: Synephrine.

Clayton South, SPN (ISSA), is a recognized expert in the bodybuilding / fitness industry with over 150 bodybuilding, fitness and nutrition publications to his credit.
Synephrine is one of the adrenergic amines that stimulates the beta-3 receptors with minimal impact on the other receptor sites. This functions to increase the metabolic rate without affecting heart rate or blood pressure. Synephrine releases adrenaline and noradrenaline only in the beta-3 receptor sites (mostly adipose tissue and the liver). Stimulation of the beta-3 receptor sites elicits the breakdown of lipolysis (fat).

Synephrine is used to activate the adrenaline system without the stimulatory effect posed by ephedra-based products.

Synephrine is a stimulant, similar to caffeine and ephedrine. It is thought to have similar effects in terms of providing an energy boost, suppressing appetite and increasing metabolic rate leading to the burning or more calories. It is used as a safer alternative to Ma Huang, synephrine is theorized to stimulate fat metabolism without the negative cardiovascular side effects experienced by some people with Ma Huang.

The most likely explanation for weight loss effects attributed to citrus aurantium (synephrine) supplements is the stimulant like effects of the alkaloids. Although this effect is likely to be somewhat less dramatic that effects induced by Ma Huang (ephedra - also known as Sida Cordifolia), users can expect variable effects including reduced appetite and heightened feelings of energy (similar to caffeine)... both of which are likely to result in weight loss.