Yohimbine (as Hydrochloride for the isolated version, or Pausinystalia bark extract for the plant extract) is a powerful stimulant which instigates release of various chemicals including the catecholamines, adrenaline and noradrenaline.
These are responsible for instigating the ‘fight or flight’ response meaning an increase in levels of usable energy in the blood (from glucose and fatty acids), increased heart rate and elevated blood pressure. Catecholamines are therefore able to mobilise fatty acids from fat cells in order for them to be oxidised.
This is not typically something worth a great deal of consideration. Fatty acids can be mobilised simply by creating a calorie deficit and if a deficit is not in place, mobilisation doesn’t improve fat loss (fatty acids which have been mobilised simply return to adipose tissue). With that said, there is more to the picture.
Fat cells have 2 different receptors relevant to this discussion, alpha-2 and beta-2 receptors. Beta receptors are the targets for various chemicals (including the afore-mentioned adrenaline), bound in order to initiate lipolysis, but the alpha receptors are considered an inhibitory system which inhibits this process. Yohimbine not only activates Beta-2 receptors via catecholamine release, it antagonises (blocks) the Alpha-2 receptors and prevents this inhibitory mechanism from taking hold. This becomes important for extremely lean individuals who have areas of fatty tissue richer in alpha receptors – often dubbed ‘stubborn fat’, as it can facilitate increased fat loss – but it is unlikely to make a significant difference in normal weight or overweight individuals looking to become leaner. Critically, yohimbine must be taken in the fasted state to have these effects, as insulin mediates B2 receptor antagonism.
On top of this, yohimbine may have the ability to blunt appetite though this is only shown in rats at present.
The recommended dosage is usually 0.2mg per kg of lean body mass, often combined with caffeine at a dosage of around 2mg per kilogram. These together have a synergistic effect of prolonging catecholamine release, and so may create a more profound effect when taken together.
When considering any stimulant, it would be prudent to consider any side effects. These include heightened blood pressure, anxiety, increased heart rate, sleeplessness and all of the immunosuppressing effects of continual catecholamine release. These will impact individuals differently, with lifestyle factors like smoking, age, sex, weight and individual genetic variants altering the magnitude of side effects and even the half life of whichever you take. For stimulant use start conservatively and only increase dosage if you perceive a need – and of course it must be said that perpetual stimulant use may simply be masking poor sleep, and that is not recommended long-term.
Seeing as yohimbine is similar to caffeine in its stimulatory effects, dosage and overuse is a prudent consideration. There might be evidence to suggest that yohimbine HCL could have a positive effect in very lean individuals training in a fasted state for increased fat loss in stubborn areas, otherwise it is a supplement outside the remit of most fat loss scenarios.