Green tea, made from the leaves of Camellia sinensis, is a popular beverage consumed over thousands of years in Asian cultures and more recently throughout the world. Research has revealed considerable health benefits of green tea's high-powered antioxidants, known as catechins, for preventing and treating a variety of health conditions.
Appetite Suppressant
In a study on breast cancer survivors, decaffeinated green tea promoted weight loss, according to a study published in the December 2010 "Journal of Human Nutrition and Dietetics." In the study, participants drank 32 oz. of decaffeinated green tea every day for six months. At the end of the study, average weight decreased by 2.6 lbs., high density lipoprotein cholesterol, or HDL, increased and insulin resistance decreased. The women also consumed significantly fewer calories during the study period, indicating that green tea has an appetite-suppressing effect independent of its caffeine content.
Short-term Effects
Antioxidant catechin molecules in green tea did not promote weight loss in a short-term study published in the February 2011 "Obesity" journal. In the study, male and female volunteers consumed three capsules per day of a supplement containing 135 mg of green tea catechin extract for two days. Resting metabolic rate was unaffected by the green tea supplement, as was metabolic response to a meal -- a measurement of the increased energy your body expends to digest and process the nutrients in food.
Synergistic Effects
The combination of catechins and caffeine in green tea may exert a synergistic effect that promotes and maintains weight loss, say authors of a study published in the April 2010 "Physiology and Behavior" journal. Green tea may act by inhibiting the breakdown of hormones that increase metabolic rate and energy production. The mixture of green tea's antioxidant catechins and caffeine increase fat burning, and preserve lean muscle mass, according to the report.
Combination With Caffeine
The "American Journal of Clinical Nutrition" reported in its January 2010 issue on a study that found green tea significantly reduces weight, body fat percentage and waist circumference. The meta study -- a review of previously published research -- looked at 15 studies, including more than 1,200 patients, and concluded that consumption of green tea catechins with caffeine decreased body mass index, body weight and waist size but not waist-to-hip ratio -- a measure of weight distribution that is thought to indicate certain risk factors for cardiovascular disease. The researchers noted that the effects of green tea with caffeine are moderate and that evidence does not support the effects of green tea catechins alone for weight reduction.
References
- "Journal of Human Nutrition and Dietetics"; Green Tea Improves Metabolic Biomarkers, not Weight or Body Composition: A Pilot Study in Overweight Breast Cancer Survivors; Stendell-Hollis N.R., et al.; 2010
- "Obesity"; Influence of Short-term Consumption of the Caffeine-free, Epigallocatechin-3-gallate Supplement, Teavigo, on Resting Metabolism and the Thermic Effect of Feeding; Lonac M.C., et al.; 2011
- "Physiology and Biology"; Green Tea Catechins, Caffeine and Body-weight Regulation; Westerterp-Plantenga M.S. et al.; 2010
- "American Journal of Clinical Nutrition"; Effect of Green Tea Catechins with or without Caffeine on Anthropometric Measures: A Systematic Review and Meta-analysis; Phung O.J., et al.; 2010
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