Diet pills, formally called appetite suppressants, can be either prescription or over-the-counter drugs. Because most are pharmacologically classified as stimulants, many are considered psychoactive or potentially addictive, and are therefore prescribed as controlled substances. Adipex -- the generic name is phentermine -- previously marketed in the United States as Fastin and Lonamin -- is one such drug. Phentermine is one of two ingredients in the discontinued diet drug Fen-Phen, a different component of which has been linked to fatal cardiopulmonary problems. Users should consult a physician before taking this medication.
Dexatrim
Dexatrim was formerly more similar to Adipex than it is today in that it contained powerful stimulant substances -- first phenylpropanolamine and then ephedra -- that both suppressed appetite and increased metabolism. Early in the new millennium, however, both of these substances were banned by the FDA owing to health safety concerns, and as of 2010 Dexatrim contains a mixture of vitamins and herbal ingredients, including caffeine and bitter orange peel extract; the latter acts similarly to ephedra.
Guarana
Guarana, derived from a plant indigenous to the Amazon basin, is used as both a flavoring agent and a weight-loss remedy. Its main ingredient is caffeine, with guarana seeds having a higher concentration of this substance than coffee beans. A 2001 study published in the "Journal of Human Nutrition and Dietetics" suggests that guarana may also prolong stomach emptying, leading to an increased sensation of fullness.
Zantrex
Zantrex contains a variety of compounds aimed at increasing metabolic rate, boosting immune function and raising energy levels. The ingredients of chief interest are yerba mate, caffeine and green tea extract, all of which, like Adipex, contribute to an elevated level of caloric expenditure. As with all preparations that contain caffeine, some weight loss may occur as a result of a diuretic effect, which looks good on the scale in the short term but is detrimental to the body's function in the long term.
Green Tea Extract
Caffeine is the main ingredient in green tea extract, which both suppresses appetite and increases metabolic rate, in addition to supplying a host of other health benefits. There is little scientific evidence, however, that green tea -- while regarded as very safe -- is superior to calorie restriction alone in the promotion of weight loss, and users sensitive to caffeine should stay away from this extract.
References
- Adipex.org: What is Adipex?
- The Diet Channel: Facts about Dexatrim
- Diet Spotlight: Zantrex Review
- Mayo Clinic: Over-the-counter (OTC) weight-loss pills: What you need to know
- Guarana.com: Everything you always wanted to know about guarana
- "Journal of Human Nutrition and Dietetics"; Weight loss and delayed gastric emptying following a South American herbal preparation in overweight patients; Andersen et al.; June 2001
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