Ostojic SM Yohimbine: the effects on body composition and exercise performance in soccer players. Res Sports Med. 2006 Oct-Dec;14(4):289-99.
The main aim of this study was to determine the effects of yohimbine supplementation on body composition and exercise performance in professional soccer players. The athletes (20 top-level male soccer players) were allocated to two randomly assigned trials. Subjects in the yohimbine group orally ingested tablets that contains yohimbine at a dose of 20 milligrams per day in two equal doses for 21 days. Subjects in the placebo group ingested an equal number of identical-looking pills that contained cellulose. There were no statistically significant changes in body mass and muscle mass within or between trials (p > 0.05) after the supplementation protocol. Percentage of body fat significantly decreased in the yohimbine group after the supplementation protocol (9.3 +/- 1.1 vs. 7.1 +/- 2.2%; p < 0.05). Furthermore, fat mass was significantly lower in the yohimbine versus placebo trial at postsupplementation assessment (7.1 +/- 2.2 vs. 9.2 +/- 1.9%; p < 0.05). There were no changes in exercise performance indicators (bench and leg press, vertical jump, dribble and power test results, shuttle run) within or between. trials (p > 0.05). No subject reported any side effects from yohimbine. The results of the current study indicate that supplementation with yohimbine combined with resistance training does not significantly alter the body mass, muscle mass, or performance indicators in professional soccer players. Nonetheless, yohimbine supplementation appears to be suitable as a fat loss strategy in elite athletes.
My comments: Yohimbe has been around for many years, first popularized by Dan Duchaine in his seminal work "Bodyopus: Militant Weight Loss and Body Recomposition" where he proposed its use for the loss of stubborn bodyfat. Myself, Elzi Volk and others have written about its use and a forthcoming book (to be written after I finish the protein book) on Stubborn Bodyfat and how to get rid of it will tell you all you ever wanted to know about it for the same purpose.
Falsely thought to raise testosterone (because it gives men erections and has been used to treat erectile dysfunction), yohimbe is an alpha-2 receptor antagonist. This means that it blocks the effects of the alpha-2 receptors.
By means of background, the body has two general categories of receptors for the catecholamine (adrenaline/noradrenaline) hormones. They are beta and alpha receptors. Beta receptors have at least 3 variants (although beta-1 and 2 are the ones found most in humans) and alpha recpeptors have two primary variants (alpha-1 and alpha-2).
Without getting into too much complexity, you can think of beta receptors as accelerators. When they are activated, they tend to increase heart rate, blood pressure, muscle force output and of interest here, fat breakdown and mobilizatoin. You can think of the alpha receptors as brakes, when activated they tend to slow things down. Of interest here, activation of alpha-2 receptors on fat cells inhibits fat breakdown.
Of even more interest, stubborn bodyfat (especially women's lower bodyfat) has been found to contain significantly more alpha-2 receptors than beta receptors. This is part of why losing lower bodyfat is so difficult. Men's abdominal and love handle fat is at least similar.
Previous studies have suggested a role for yohimbe for fat loss but none have used athletes, hence this study. Recruiting male soccer players, the subjects received either 20 mg of yohimbine per day (in two divided doses) or a placebo and were placed on the same periodized training program (not described in the paper, unfortunately). Diet was uncontrolled which is one major limitation of the study. A number of fitness tests (bench and leg press, vertical jump, dribble and power test results, shuttle run) were done in addition to bodyfat as measured by 7 site skinfold. The fitness tests were run because of the (false in my opinion) belief that yohimbe is anabolic or improves training. The study lasted 21 days.
The subjects weighed 81 kg and started at approximately 9% bodyfat for both groups, other aspects of the subjects were also nearly identical between groups. This means that the yohimbine dose was slightly higher than the typically used/recommended .2 mg/kg dose (typically a 81 kg subject would take 16 mg/day).
Over that time period, there were no significant differences in changes in the fitness status of the subjects; all improved about equally. However, there was a difference in fat mass with the yohimbine supplemented subjects dropping from 9.3 to 7.2% bodyfat (the placebo group went from 8.9 to 9.2% but this wasn't statistically significant). And while bodymass did go up slightly in the yohimbe group, this is probably due to yohimbe's tendency to cause water retention more than anything else. No side effects were reported.
Frankly, that's a pretty major fat loss for such a short period of time with no (apparent) change in diet. As above, since diet was uncontrolled, it's impossible to know if the yohimbine group did change their diet. There is some evidence that yohimbe may affect satiety and food intake so it's possible that the supplement group reduced their food intake; coupled with the training program this could explain the fat loss.
However, the point still stands, whether the yohimbe worked by inhibiting alpha-2 receptors and mobilizing stubborn bodyfat or causing a spontaneous reduction in food intake, the fat loss still occurred.
I should mention that a lack of side-effects is not a universal report, this is especially true if yohimbe bark (as opposed to pure yohimbine HCL) is used. The various alkaloids in herbal yohimbe can cause a myriad number of side effects including chills, nausea, tremors and panic. High dose yohimbe is also used to induce anxiety attacks and people prone to such should probably stay the hell away from it. Given that its fairly easy to obtain pure yohimbine HCL, the herbal should be unnecessary in the first place. I used to use the old Twinalb Yohimbe fuel and the side effects were there. Pure yohimbine HCL (I've used the Primaforce brand) doesn't generate nearly the same issues. Note that yohimbine HCL can only be sold in amounts of 2.5 mg per pill so you end up having to take a bunch of them at once.
Starting with a half dose to assess tolerance is still probably the best approach. I also dont feel that splitting the dose across the day is the best way to use it; I prefer a combination of yohimbe and caffeine 30-60 minutes before aerobic training. The yohimbe/caffeine mobilized fatty acids which are then burned off during the cardio. You'll have to wait for my stubborn bodyfat book for more details than that.