Guarana is a shrub or woody vine that appears in many weight loss formulas because it contains Caffeine
. Few studies have isolated the independent effects of guarana and the mechanism of action. In addition to caffeine, guarana contains other bioactive substances like tannins and theobromine and theophylline. In this recent study by Brazilian researchers, they examined the effects of guarana extract on fat metabolism in sedentary and exercise-trained rats. They used two doses of extract and also compared this two guarana with the caffeine content removed. After 14 days, the highest dose of guarana extract resulted in a significant reduction in food intake, but this was not the case with the lower dose or the decaffeinated extract. Guarana extract at the highest dose also resulted in a significant increase in an enzyme called CPTI. This is the enzyme responsible for transporting fat into the mitochondria where it is burned. The results support the general use of guarana as a potential weight loss agent and the increase in CPTI suggests that in addition to reducing food intake it may also enhance fat oxidation. Future studies should be done to confirm these findings in overweight subjects.
Lima WP, Carnevali LC Jr, Eder R, Costa Rosa LF, Bacchi EM, Seelaender MC. Lipid metabolism in trained rats: Effect of guarana (Paullinia cupana Mart.) supplementation. Clin Nutr. 2005 Sep 21; [Epub ahead of print]