The main effect of caffeine is thermogenic, which has already been discussed. However, another significant effect of this substance on body composition is related to its action on adenosine receptors on adipocytes. More specifically, the activity of these is such that it promotes fat retention within the fat cells, so caffeine, by inhibiting them, promotes their emptying. Once again, with regard to the side effects, form and dosage of guarana supplements, please refer to the section on thermogenic substances.