People seeking help with weight loss frequently turn to stimulants, which may help increase calorie burn and give you the energy to exercise, which can accelerate your progress. In fact, stimulants are the only over-the-counter substances that have been shown to have any significant effect on weight loss at all. They are not without risk -- ephedrine and phenylpropanolamine, the two most effective weight loss stimulants, were banned by the U.S. Food and Drug Administration after reports of serious side effects and sudden deaths. Some stimulants remain, however, although none is considered harmless.
Caffeine is the world's most common stimulant, and it is the foundation upon which all other stimulants are based. Mayo Clinic nutritionist Katherine Zeratsky says that it may have a small effect on weight loss by increasing calorie burn and suppressing your appetite, but long-term use has never been shown to be an effective weight loss aid. Some people are sensitive to caffeine and experience nervousness and tremors with even the smallest exposure -- these people should not use stimulants of any kind. Even if you're not sensitive, caffeine can cause anxiety, insomnia and chronic stress in high doses.
Guarana is an herbal stimulant, and another common diet pill ingredient. It contains caffeine, as well as theobromine and theophylline, which may reduce your appetite and increase your energy. Guarana has been shown to be an effective weight loss aid, but it isn't benign -- it can cause heart arrhythmia, and high doses can cause seizures and death. If used in combination with caffeine, lower doses of guarana can cause negative and potentially dangerous side effects. Many energy drinks contain guarana, so read labels before you mix supplements with stimulants.
Yerba mate is another herbal stimulant, but it is more commonly ingested as a tea rather than in pill form. It contains caffeine, theobromine and theophylline like guarana, but it also contains phytochemicals that may assist in weight loss. Yerba mate works as an appetite suppressant, but it also forces your stomach to retain food longer, making you feel full for a longer time after eating. Long-term use is associated with an increased risk of certain cancers, but even small amounts can cause anxiety, restlessness and insomnia. People with heart disease, high blood pressure or anxiety disorders should not use yerba mate.
Green tea is the most benign stimulant of the bunch. It is nothing more than the familiar tea leaf, harvested while young and green to obtain the highest levels of antioxidants possible. These antioxidants have been shown to aid in weight loss by increasing fat oxidation and metabolism, and the natural levels of caffeine provide a mild stimulant effect. You can reap the weight loss benefit whether you drink tea made from the whole leaf or take an extract of epigallocatechin gallate, the active antioxidant in green tea. Drinking the tea, however, confers additional benefits such as protection against cavities. The University of Maryland Medical Center notes that drinking green tea is associated with a lower risk of death from any cause.