Researchers at Penn State looked specifically at a compound found in most green teas—epigallocatechin-3-gallate (EGCG)—to determine its effects on weight gain. Two groups of obese mice were fed a high-fat diet, but only one group also ate EGCG. Compared to the control group, the mice consuming EGCG in addition to the high-fat diet gained weight 45 percent more slowly. The mice fed the green tea supplement also appeared to be absorbing less fat (based on an increase in fecal lipids). Interestingly, both groups of mice ate about the same amount of high-fat food, suggesting that EGCG does not suppress appetite.

“There seems to be two prongs to this,” says lead researcher Dr. Joshua Lambert, assistant professor of food science in agricultural sciences. “First, EGCG reduces the ability to absorb fat and, second, it enhances the ability use fat.”

It is significant that the mice in this study were obese to begin with, which, in Lambert’s opinion, makes this study more relevant to humans, who often don’t begin to consider their weight until they begin to have problems associated with obesity.

But here’s the caveat: It’s going to take more than one cup of tea to consume amounts of EGCG equivalent to that consumed by the mice—10 cups to be precise. But according to Lambert, recent studies examining the effects of green tea in humans suggest that drinking even a cup or two of green tea per day may be enough to have a positive effect on body weight.