Consumption of green tea has been associated with a number of positive effects on health. Several studies have shown regular use of green tea can aid fat loss. Green tea is believed to augment norepinephrine, a hormone that promotes fat breakdown. Other possible benefits of green tea include decreased food intake and decreased formation of fat.
Polyphenols, the bioactive compounds in green tea, account for a third of the dry weight of the leaves. The predominant polyphenols are the catechins including epicatechin, epicatechin-3-gallate, epigallocatechin and epigallocatechin-3-gallate (EGCG). Most research has focused on EGCG as the predominant polyophenol.
German researchers recently tested the effects of EGCG rates of carbohydrate and fat oxidation. Subjects consumed either 300 mg of EGCG or placebo in a fasted state and after a standard meal. Compared to placebo, supplementation with EGCG caused a shift in energy utilization from carbohydrate to fat oxidation. The effect was more pronounced after eating a meal. In the placebo trial, only 30% of the total energy burned after the meal was attributed to fat, whereas 54% of the energy burned came from fat oxidation after EGCG supplementation.
These results show supplementation with 300 mg EGCG encourages use of fat over carbohydrate as fuel, which provides a plausible mechanism to explain the anti-obesity effects of green tea.
Reference: J Am Coll Nutr. 2007 Aug;26(4):389S-395S.
Jeff S. Volek is currently an associate professor in The Human Performance Laboratory at The University of Connecticut, Storrs, CT. He is an R.D. and has a Ph.D. in Kinesiology (Pennsylvania State University). He serves on the editorial boards of Nutrition and Metabolism, Medicine and Science in Sports and Exercise and the Journal of Strength and Conditioning Research. He has published over 150 scientific articles and chapters.