Drinking green tea before exercise could help burn fat. American scientists carried out studies on 12 healthy young men, who took either green tea extract (GTE), equivalent to 3.5 cups of tea, or placebo before taking part in cycling trials. Average fat oxidation rates were 17% higher in the green tea group and the contribution of fat oxidation to total energy expenditure was also significantly higher.

In a second experiment, 11 healthy men took an oral-glucose-tolerance test before and after supplementation with capsules containing either GTE or placebo. Ingestion of GTE was found to increase insulin sensitivity by 13%, meaning that it could potentially reduce the risk of type 2 diabetes.

Green tea extract ingestion, fat oxidation, and glucose tolerance in healthy humans. Am J Clin Nutr. 2008 Mar;87(3):778-84.