There are many known health benefits of consuming green tea such as improving heart health and preventing chronic diseases and cancer. These benefits result from the antioxidant properties of chemicals called polyphenols found in high concentrations in green tea plants. Green tea extract is essentially green tea leaves processed as a supplement that contains a higher concentration of the polyphenols than found in a regular cup of green tea. In addition to general health benefits, supplementing green tea extract may increase fat loss and improve exercise performance by reducing muscle soreness experienced after exercise. (Jowko 2015)
The main components of green tea are polyphenol catechins or phytochemicals found from plant sources that serve as antioxidants. The most abundant catechin source in green tea is epigalocatechin gallate (EGCG) and standardized green tea extract supplements provide higher and more constant levels of EGCG to utilize its beneficial effects. (Jowko 2015)
The mechanisms for which EGCG contributes to greater fat loss are by increasing fat oxidation and energy expenditure during exercise. EGCG inhibits the enzymes that break down norepinephrine allowing for prolonged stimulation of the sympathetic nervous system, which controls thermogenesis and fat metabolism (Jowko 2015). EGCG may also improve exercise performance by reducing muscle soreness following exercise allowing for better recovery. Intense exercise induces oxidative stress, and antioxidant supplementation with green tea extract may be an effective strategy to reduce oxidative stress and subsequent muscle damage. (Jowko 2015)
Consumption of green tea extract, especially in combination with caffeine, has been shown to increase fat oxidation and energy expenditure in both sedentary and physically active persons during exercise (Jowko 2015). A systematic review of EGCG effects on energy expenditure and fat metabolism concluded that even low doses of EGCG (300 mg/day) moderately increases energy expenditure and respiratory quotient that may lead to greater fat oxidation and weight loss (Kapoor 2017). Furthermore, chronic but not acute ingestion of green tea catechins increases the antioxidant potential in plasma and can alleviate oxidative stress and muscle damage caused by strenuous exercise (Jowko 2015).
Most green tea extract supplements are standardized to 50% EGCG, meaning a 500mg dose would contain 250mg of EGCG. The benefits for fat loss and improved recovery depend on the catechin content so higher doses of green tea extract may be needed to obtain the higher amounts of EGCG. While no optimal dose or side effects have been established for EGCG supplementation, beneficial effects are seen at higher doses of 400-500mg of EGCG daily. However, Kapoor (2017) noted no dose response effect of EGCG observed on energy expenditure and fat oxidation, suggesting dosage is not a significant moderator. (Jowko 2015, Kapoor 2017)
Jówko, E (2015). Green Tea Catechins and Sport Performance. Antioxidants in Sport Nutrition. Boca Raton (FL): CRC Press/Taylor & Francis. Chapter 8. Kapoor MP, Sugita M, Fukuzawa Y, Okubo T (2017).
Physiological effects of epigallocatechin-3-gallate (EGCG) on energy expenditure for prospective fat oxidation in humans: A systematic review and meta-analysis. The Journal of Nutritional Biochemistry, 43, 1-10.