Drinking green tea can help reduce weight without increasing heart rate or blood pressure, according to a mini-review by researchers at the Chinese Academy of Sciences.
The authors reviewed experimental studies, clinical studies and in vitro studies. The human studies reviewed (which involved a daily total of 375 mg of catechins with 270 mg of EGCG and 150 mg of caffeine) showed that green tea consumption led to a significant increase in energy expenditure, decrease in body weight, decrease in waist circumference, and no change in heart rate or blood pressure. In vitro studies show that green tea extract stimulates thermogenesis (energy production).
The results of this review suggest that consumption of green tea may have a role to play in reducing body weight. The authors conclude, "Further studies are necessary to evaluate the observed weight-reducing action of green tea extract, especially in patients with much greater obesity."
Catechins, flavonoid antioxidants found in green tea, are thought to be responsible for many of its health benefits. Black tea has them too, but in lower amounts.
Source: Journal of Medicinal Food, 2006 Winter; 9(4): 451-8