Thermogenesis and metabolic rate increase
Synephrine activates beta-3 adrenergic receptors in adipose tissue and brown fat, increasing thermogenesis and metabolic rate. Clinical studies show modest increases in energy expenditure (65–100 kcal/day) with synephrine supplementation — a meaningful but smaller effect than ephedrine, consistent with its lower receptor potency.
Fat mobilization and lipolysis
By activating beta-3 adrenergic receptors in adipose tissue, synephrine stimulates lipolysis — releasing stored fatty acids for oxidation. Combined with exercise, this fat mobilization effect may enhance fat burning during aerobic activity, particularly in a fasted state.
Athletic performance and appetite reduction
Synephrine modestly increases athletic performance and reduces appetite through adrenergic receptor activation. Effects are more modest than ephedrine but come with a substantially lower cardiovascular stimulant risk profile when used alone at standard doses.
Beta-3 adrenergic receptor agonism
Unlike ephedrine which activates all three beta-adrenergic subtypes (beta-1, -2, -3) and alpha receptors producing strong cardiovascular effects, synephrine preferentially activates beta-3 receptors in adipose tissue — producing thermogenic lipolysis with less cardiac (beta-1) and bronchodilatory (beta-2) stimulation at standard doses.
Modest MAO inhibition
Synephrine mildly inhibits monoamine oxidase, modestly increasing catecholamine availability. This mild MAO inhibition is generally not clinically significant at supplement doses alone but can become relevant when combined with other sympathomimetics or certain medications.
Alpha-adrenergic and serotonin receptor interaction
Synephrine has activity at alpha-1, alpha-2, and serotonin 5-HT2 receptors — complex receptor pharmacology that contributes to its vasopressor effects and the cardiovascular stimulation observed when doses exceed 50 mg/day or when combined with caffeine.
Randomized crossover study examining synephrine (50 mg) effects on energy expenditure and fat oxidation in healthy adults.
Healthy adults. Crossover metabolic assessment.
Synephrine 50 mg significantly increased resting energy expenditure (~65 kcal/day) and fat oxidation vs. placebo. No significant changes in heart rate or blood pressure at this dose. Effects enhanced when combined with naringenin from bitter orange.