There has been a recent explosion of energy pills on the market intended for people trying to lose weight, athletes looking to improve performance, or those looking for more energy to get them through the day. Due to the untested nature of many of these products, it can be difficult to determine the efficacy and safety of long-term use. However, we can draw some generalizations based upon what we know about the ingredients and their effects on the human body. Most energy pills contain combinations of natural herbs and essences which are metabolized by the body into energy-producing chemicals. Some of these include ma huang, guarana, kola nut, and ginseng. Ma huang is a natural source of the chemical ephedrine, and guarana and kola nut contain high levels of caffeine.