Fat burners fall under the nutritional category of thermogenic’s. They are substances, often containing ephedrine, caffeine, and aspirin (although aspirin is rarely used today), designed to help promote lipolysis in the body. It other words, they are designed to break down body fat to be used by the body as energy. They also stimulate the body’s central nervous system leaving you with the “jitters” after taking one of these pills. You can thank the caffeine for that!