Green tea has become a popular weight loss supplement. Clinical studies suggest that green tea extract may increase metabolism and help burn fat. Researchers speculate that substances in green tea known as polyphenols, specifically the catechins (particularly epigallocatechin gallate), may be responsible for this fat burning effect.
In one study, researchers pooled the results of 11 studies in a meta-analysis to find out whether or not green tea has the ability to regulate body weight.
They found that catechins did significantly decrease and maintain body weight, although the result was not significant for those who regularly consumed more than 300 mg of caffeine per day.
The researchers concluded that catechins or a catechin-caffeine combination may have a positive effect on weight loss and weight management.