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According to Integrative Medicine, a recent clinical study has indicated that green tea extract may offer significant weight loss benefits. The trial studied the possible effects of green tea on daily energy expenditure and fat oxidation in humans. On three occasions, 10 healthy male participants were randomly given one of either green tea extract, caffeine or placebo three times a day. Researchers concluded that green tea extract possessed certain thermogenic properties and promoted the oxidation of fat via a mechanism unrelated to its caffeine content. (The study was originally published in the American Journal of Clinical Nutrition.) In a study from the University of Geneva in Switzerland , which appeared in the December 1999 American Journal of Clinical Nutrition, researchers used a respiratory chamber to measure the energy expenditure and respiratory quotient (an indication of which components of food-fats, carbohydrates or protein- the body burns for energy) of 10 healthy young men. Three separate times, the men randomly took one of the following as a daily total:
- Green tea has thermogenic properties and promotes fat oxidation; these properties are not explained by its caffeine content alone.
- Green tea extract may affect body composition via the sympathetic nervous system's activation of thermogenesis, fat oxidation, or both. On 3 occasions, 10 healthy men (mean age = 25[pm]1 years, mean body mass index = 25.1[pm]1.2) underwent measurement of 24-hour energy expenditure (EE), respiratory quotient (RQ), and urinary excretion of nitrogen and catecholamines in a respiratory chamber. On the 3 occasions, subjects received capsules containing green tea extract (50 mg caffeine and 90 mg epigallocatechin gallate), caffeine (50 mg), or placebo in random order; doses were equally divided among 3 meals.
- Green tea extract also contains other catechins but epigallocatechin gallate constitutes [geq]50% of the total and is believed to be the most pharmacologically active. Compared with placebo, treatment with green tea extract significantly increased 24-hour EE (+4%) and significantly decreased mean 24-hour RQ (from 0.88 to 0.85) without any change in urinary nitrogen excretion. (The decrease in RQ reflects an increase in oxidation of fat relative to carbohydrate.) Compared with placebo, treatment with green tea extract resulted in higher 24-hour urinary norepinephrine excretion (+40%). Treatment with caffeine alone had no effect on EE, RQ, or urinary excretion of nitrogen or catecholamines.
1) Standardized green tea extract (containing 375 milligrams total catechins and 150 milligrams of caffeine) 2) 150 milligrams of caffeine 3) PlaceboThe Results: The men who got green tea saw their daily energy expenditures increase an average of 78 calories compared to placebo (in this study, caffeine was no better than placebo). The green tea also altered respiratory quotients, indicating a shift toward more fat burning. Yet the green tea did not increase heart rates, a dangerous consequence of some other weight-loss remedies. The Reason: Researchers credit the boost in metabolism to tea's catechins, which inhibit an enzyme that breaks down norepinephrine (a brain chemical that speeds metabolism and fat burning). The result prolongs the chemical's metabolism-boosting effects, and combined with the added benefits of the antioxidant components, this product is an excellent alternative to outmoded thermogenic enhancement products.