It seems like there are a variety of diet pills on the market today, but in reality many of these pills have similar ingredients with one or two changes. The medical community has chosen to categorize diet pills as simply prescription pills and nonprescription pills. Non prescription pills are over-the-counter and usually contain herbal supplements to help suppress the appetite, increase the metabolism or keep the body from absorbing carbs and starches amongst other qualities.

In general it's thought that nonprescription pills are less effective than prescription pills but that may simply be because there are far fewer clinical studies performed on weight loss supplements than on prescription pills created by large drug companies. It is important to review each and every ingredient in the diet pills you purchase because some of them may simply be 'snake oil' as they say.

Some ingredients that are typically shown or suggested to have an effectiveness are Guaruana extract; also called guaranine (a form of caffeine) Gotu Kola Nut which also contains caffeine, Bitter orange which stimulates the body's metabolism, Ma Huang contains ephedrine which also stimulates the metabolism and Hoodia Gordinii. Hoodia Gordinii is a cactus found in South Africa and is showing a lot of potential as an appetite suppressant. Early trials suggest is can reduce the appetite by as much as fifty percent. A couple of large drug companies are trying to synthesize the chemical in Gordinii to create a copyrighted prescription form of this supplement.

There are other herbal supplements used in diet pills for their effectiveness, but again it is best to look up each listed and make sure there aren't any warnings associated with it. The FDA doesn't currently regulate the making and selling of dietary supplements so it's easy for a slick marketer to set up a company.