Once upon a time, there was a weight loss aid called Ephedra. It was sourced from the plant ma huang. What it did to the human body was use alpha-2 receptors that acted as a central nervous system (CNS) stimulant. As with all CNS stimulants, the body adapted to it rapidly, and the longer you took it, the longer it took to get the desired effect. The only problem with doing this with Ephedra and more potent CNS drugs is the other effects. One of the most important, and the reason Ephedra was recommended for weight loss, is that it increases body temperature. And the hotter the body runs, the more calories are expended. The dangerous effect of this, however, is that as body temperature increases, so do blood pressure and heart rate.