Also called guarana, this extract is used primarily in herbal supplements and beverages as a stimulant. In animal studies (mice), it has been shown to affect fat metabolism. There is also research showing that repeated use of guarana can result in persistent increases in heart rate and blood pressure as well as in unfavorable actions on glucose and potassium homeostasis. Such effects could be detrimental in persons with hypertension, atherosclerosis, or glucose intolerance—conditions that are strongly associated with obesity.
Guarana is sometimes used in cellulite products because of its theophylline and caffeine components. Research has shown it can be absorbed into the skin. Whether or not topical application can affect fat metabolism or have other associated health risks in humans is not known (Sources: International Journal of Pharmaceutics, April 2006, www.sciencedirect.com/; Food and Chemical Toxicology, June 2006, pages 862–867; Clinical Nutrition, December 20005, pages 1019–1028; and Clinical Pharmacology & Therapeutics, June 2005, pages 560–571).