According to the Mayo Clinic, there are no diet pills available that work incredibly fast, especially not without a person's added efforts to eat less and exercise more. Redbook Magazine lists Alli, Glucophage and Byetta as diet pill options that have been proven effective, but it also warns that side effects associated with the use of these drugs can be alarming. WebMD says the same about Belviq, phentermine and Qsymia.
The Mayo Clinic lists additional over-the-counter treatments that are available to aid weight loss, but most treatments are ineffective or lack sufficient evidence to evaluate. Examples include bitter orange, chitosan, chromium, conjugated linoleic acid, guar gum, hoodia and green tea extract. Diet pills work in a variety of ways. Redbook explains that some diet pills, like Alli, prevent the body from digesting a large portion of the fat that a person consumes. Instead, the fat is passed through stools. Glucophage and Byetta were originally developed as diabetes drugs but are also being used to treat obesity. Glucophage helps to suppress the appetite, and Byetta slows the movement of food into the small intestine from the stomach. Doctors often prescribe these two drugs together for weight loss. According to WebMD, Belviq, phentermine and Qsymia also work by decreasing the appetite. Qsymia actually contains phentermine and another drug, called topiramate, which is believed to help the body burn calories.