By Jennifer Copley (Last Updated 25 September 2008)
In addition to its anti-cancer and heart-protective properties, research indicates that green tea can aid weight loss by increasing endurance and fat oxidation.
Green tea contains catechin polyphenol compounds, which can boost the metabolism. Black, oolong, green, and white teas all come from the same Camellia sinensis plant, and all contain these beneficial ingredients. However, because green tea leaves are steamed rather than fermented as with black and oolong teas, more polyphenols are preserved.
Increased Rate of Fat Burning
Catechin polyphenols increase the rate of thermogenesis (the production of heat via increased metabolic rate) and fat oxidation, even when the body is at rest. In other words, the body is more inclined to burn fat for fuel, not only during exercise, but also while sedentary. Other effects include:
- Decreased fat absorption
- Increased fat excretion
- Appetite suppression
Noteworthy Research Studies
Dullo et al’s (2000) study of 10 subjects compared green tea extract to a placebo. The green tea group increased their energy expenditure by 4%, thus burning more calories. To determine whether the effect was caused by the caffeine in the tea, another group of subjects were given caffeine supplements equivalent to that found in the green tea. The caffeine group did not increase their energy expenditure or rate of fat oxidation with caffeine alone.
A study conducted by Kao Corp’s Biological Sciences Laboratories researchers in Japan (2005) found that green tea could boost athletic endurance by up to 24%. Mice that were given a quantity of green tea extract that was equivalent to a person drinking approximately 4 cups of green tea per day achieved 8-24% improvements in endurance after just 10 weeks, thus increasing the capacity for exercise and calorie burning.
In the Kao Corp study, researchers reduced the caffeine content of the supplements given to ensure that the effects weren’t attributable to caffeine. They also observed the effects of single doses of green tea extract, which did not generate the same benefits; only long-term consumption was effective in increasing endurance.
A 2008 study conducted by Venables et al. found that fat oxidation rates in a group of subjects who consumed green tea extract were 17% higher than among those who were given a placebo. Increasing the fat burn rate to this extent could provide a significant boost for weight loss efforts. However, benefits are more likely to be realized by those who engage in vigorous exercise and eat nutritious food as well.
Optimum Dose for Weight Loss
Studies indicate that those drinking green tea for weight loss should consume at least 3 cups each day. Steeping tea for longer increases the concentration of beneficial polyphenols, but also the amount of caffeine, which may cause anxiety, restlessness, or insomnia in some people if they drink too much. Recommended steeping time for maximum health benefits is at least 5 minutes for most green teas, but some brands are stronger than others.
Decaffeination processes often remove most of the polyphenols from green tea, though natural decaffeination methods (using CO2) retain the majority of these beneficial compounds. However, for weight loss, caffeinated green tea is more effective, possibly because the interaction between the caffeine and polyphenols increases thermogenesis.
Those who are sensitive to caffeine but wish to drink caffeinated green tea for weight loss should cut out chocolate, soft drinks, and coffee to lower daily caffeine intake from other sources. Drinking green tea with meals rather than on an empty stomach can decrease the likelihood of becoming jittery.
Other Camellia Sinensis Teas May Provide Similar Benefits
While green tea is not fermented at all, oolong tea is only partially fermented, and recent studies suggest that oolong tea may also increase fat oxidation.
White tea, the least processed of all the Camellia sinensis teas, has not been studied as extensively as green tea. Studies that have been conducted have for the most part focused on anti-cancer and other health-protective properties rather than weight loss. Given that white tea is also unfermented, it’s quite possible that it has similar fat-burning effects. However, at this time there has not been sufficient research conducted to support this hypothesis.
- Dullo, A.G., Duret, C., Rohrer, D., Girardier, L. Mensi, N., Fathi, M., Chantre, P., & Vandermander, J. (2000). “Efficacy of a Green Tea Extract Rich in Catechin Polyphenols and Caffeine in Increasing 24-H Energy Expenditure and Fat Oxidation in Humans.” American Journal of Clinical Nutrition, 72(5), 1232-1234.
- Komatsu, T., Nakamori, M, Komatsu K, et al. (2003). “Oolong Tea Increases Energy Metabolism in Japanese Females.” Journal of Medical Investigation, 50(3-4), 170-175.
- Pennington Nutrition Series, No. 9. (2007). “Green Tea.” Pbrc.edu.
- ScienceDaily.com. (27 January 2005). “Green Tea Extract Boosts Exercise Endurance 8-24%, Utilizing Fat As Energy Source.”
- Shulman, J., Dr. (n.d.). “Which Teas You Should Be Drinking: The Health Benefits of Tea.” CanadianLiving.com.
- Venables, M.C., Julston, C.J., Cox, H.R., & Jeukendrup, A.E. (2008). “Green Tea Extract Ingestion, Fat Oxidation, and Glucose Tolerance in Healthy Humans.” American Journal of Clinical Nutirion, 87(3), 778-784.