Green tea extract
is a central ingredient in many diet products.
It's high in bioactive polyphenols like EGCG that have been shown to increase fat burning after ingestion and promote greater
. Similar to green tea extract, there is a solid base of research supporting multiple positive metabolic effects of caffeine including increased thermogenesis and fat oxidation. How these supplements work along and together has not been studied in great detail so German researchers performed a study that examined the short-terms effects on measures of fat burning. In a double-blind cross over study, obese men supplemented daily for 3 days with either placebo, 300 mg EGCG, 600 mg EGCG, 200 mg caffeine, or 300 mg EGCG/200 mg caffeine. On Day 3 of supplementation they rested quietly for 8 hours while measures of fat oxidation were made before and after a standardized meal. Fasting measures of fat oxidation were increased for the low dose EGCG (8%), high dose EGCG (15%), caffeine (26%), and combined EGCG/caffeine (35%) trials. Measures of fat oxidation after the standardized meal were increased for the low dose EGCG (33%), high dose EGCG (20%), caffeine (35%), and combined EGCG/caffeine (49%) trials. Both short-term supplementation with EGCG and caffeine alone were effective at increasing fat oxidation. Maximal fat oxidation rates were achieved with supplementation of EGCG and caffeine combined.
. Thielecke F, Rahn G, Böhnke J, Adams F, Birkenfeld AL, Jordan J, Boschmann M. Epigallocatechin-3-gallate and postprandial fat oxidation in overweight/obese male volunteers: a pilot study. Eur J Clin Nutr. 2010 Jul;64(7):704-13.