The use of green tea to improve exercise performance – a literature review

Background and aims: Strategies that encourage muscle cells to oxidise fat in preference to other substrates are of particular interest to athletes engaged in endurance sports and for those who use exercise as part of a weight loss regime. Studies that have tested green tea as a supplement to enhance fat oxidation have mixed results. The objective of this article is to review systematically trials that investigated the effects of green tea on fat oxidation during exercise in adults. Methods: A comprehensive search of PubMed, Web of Science, CINAHL, Sports Discus, Science Direct and unpublished data was performed throughout April 2016. Papers that provided results of substrate utilisation studies were grouped according to observed effects and then data analysed using RevMan 5.3. Results: Eleven papers were included in the review, and eight papers were used to pool data for further analysis. All studies had at least two arms, a treatment and a control arm – ten used placebos and one used water as their control. Significant increase in fat oxidation during exercise was shown in the untrained population (p=0.03, CI -0.12 to -1.89) but not in the trained population (p=0.43, CI -0.60 to 1.41). Heterogeneity was high across both groups (Untrained participants: I2 71%; trained participants I2 77%). Conclusions: Green tea may enhance fat oxidation in people who are untrained in sports and exercise, but evidence to date does not indicate that it significantly makes a difference in well-trained individuals. However, better quality studies with more participants are required