Benefits
Body fat in one small 21-day trial in athletes
In a placebo-controlled trial, 20 professional male soccer players took 20 mg of yohimbine a day for 21 days alongside training. Body fat fell from 9.3% to 7.1% and was lower than in the placebo group afterwards, but body mass and muscle mass did not change significantly. This single trial in lean athletes says little about weight management in other adults.
Erectile function in prescription yohimbine trials
Pooled trials of yohimbine taken as a medicine by men diagnosed with erectile dysfunction found better erectile function than placebo (odds ratio 3.85 across 7 trials; 2.08 for yohimbine alone in a later analysis of 8 trials), but no significant gain in overall sexual function with yohimbine alone. These were drug trials; over-the-counter yohimbe products vary widely in content.
Exercise performance: no change in the cited trial
In the same 21-day trial in 20 soccer players, bench press, leg press, vertical jump, dribbling, power and shuttle-run results did not change within or between the yohimbine and placebo groups.
Mechanism of action
Alpha-2 adrenergic receptor blockade
Yohimbine selectively blocks pre- and postsynaptic alpha-2 adrenergic receptors, acting in both the central and peripheral nervous systems. This stimulant action underlies both its studied uses and side effects such as fast heartbeat, high blood pressure and anxiety.
Other receptor targets
Yohimbine also binds serotonin 5-HT1A and 5-HT1B receptors and some dopamine receptors (D2 and D3), with alpha-2 receptors its strongest target.
Clinical trials
Randomized, placebo-controlled trial: yohimbine 20 mg a day in two doses versus cellulose placebo for 21 days, with training (Ostojic 2006, Res Sports Med).
20 top-level male soccer players, already lean. No women and no overweight adults were studied.
Body fat fell from 9.3% to 7.1% with yohimbine and was lower than placebo after supplementation (7.1% versus 9.2%). Body mass and muscle mass did not change significantly, and exercise tests (bench and leg press, vertical jump, dribble, power, shuttle run) did not change within or between groups. No side effects were reported, but 20 people over 21 days is far too small to detect yohimbine's known cardiovascular risks.
Systematic review and meta-analysis of 7 randomized, placebo-controlled trials of yohimbine monotherapy (Ernst et al. 1998, J Urol).
Men with erectile dysfunction, a medical condition, treated with yohimbine as a medicine.
Yohimbine was superior to placebo (odds ratio 3.85, 95% CI 2.22 to 6.67), and serious adverse reactions were infrequent and reversible. This is drug research; it does not test yohimbe bark supplements or healthy men.
Systematic review and meta-analysis of 8 randomized controlled trials comparing yohimbine, alone or combined with other agents, with placebo or no treatment (Wibowo et al. 2021, Turk J Urol).
Men with erectile dysfunction in 8 randomized trials.
Yohimbine alone improved erectile function versus placebo (OR 2.08, 95% CI 1.30 to 3.32) and combinations more so (OR 6.35). Yohimbine alone did not significantly improve overall sexual function (P=0.07); only combinations did.