Green tea may speed up your metabolism and help you reduce body fat. Preliminary research suggests that green tea increases calorie burning and fat burning and counteracts the decrease in metabolic rate during weight loss. Initial human studies using green tea show promising results, but further research is needed. As with any supplement, consult your doctor before using green tea.
Background
Like all true teas, green tea comes from Camellia sinensis leaves and contains caffeine. Its potential for elevating metabolism and promoting weight loss may come from the combination of green tea's catechins and caffeine, according to a review of green tea's effects on body-weight regulation by a researcher from the Netherland's Maastricht University published in the April 2010 "Physiology and Behavior." Green tea provides a rich source of polyphenols, chemicals that plants produce to protect themselves.
Polyphenols
Because green tea isn't fermented like oolong and black tea, it retains more catechins, the polyphenols present in tea. EGCG is the most active catechin in green tea, according to the University of Maryland Medical Center.
Depending on the specific green tea, two to three cups contain 240 to 320 mg of polyphenols, according to the University of Maryland Medical Center. An adult dose of standardized green tea extract is 100 to 750 mg per day.
Research
Overweight and obese women and men who consumed a green tea catechin beverage and engaged in 180 minutes or more of moderate intensity exercise per week for 12 weeks lost more weight than a control group, researchers from Provident Clinical Research reported in the February 2009 issue of "The Journal of Nutrition." The participants drank a beverage containing 39 mg of caffeine and 625 mg of catechins. In addition to weight loss, the subjects who drank the green tea catechin beverage lost significantly more abdominal fat than the control group. The researchers concluded that the beverage enhances exercise-induced abdominal fat loss.
Considerations
Pay attention to your overall caffeine intake to avoid side effects. Although green tea contains only one-third to one-half as much caffeine as black tea, ingesting too much caffeine can result in tremors, palpitations, tension, anxiety and difficulty sleeping. Pregnant and breastfeeding women and people with heart problems, kidney disorders, ulcers or anxiety should avoid green tea, the University of Maryland Medical Center advises.
Moderately restricting calories and increasing physical activity promote lasting weight loss. Although using green tea to promote weight loss may have benefits if you make lifestyle changes to support healthy weight loss, using green tea without diet or exercise is unlikely to provide noticeable results.
References
- "Physiology and Behavior"; Green Tea Catechins, Caffeine and Body-Weight Regulation; M.S. Westerterp-Plantenga; April 2010
- "Agricultural Research"; Brewing Up the Latest Tea Research; Rosalie Marion Bliss; September 2003
- University of Maryland Medical Center: Green Tea
- "The Journal of Nutrition"; Green Tea Catechin Consumption Enhances Exercise-Induced Abdominal Fat Loss in Overweight and Obese Adults; K.C. Maki, et al.; February 2009
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