In the study, mice were fed a high-fat diet for 16 weeks. Those that also consumed green tea extract and exercised regularly were found to have just a quarter of the lipid deposits in their livers, compared to those seen in the livers of a control group of mice. Mice that were treated with only green tea extract or with only exercise had roughly half as much fat in their livers as the control group. Additionally, the researchers measured the protein and fat content in the feces of the mice, and found that those who consumed green tea extract and exercised had higher fecal lipid and protein levels.
Related: Drinking Tea May Lead to Longer Life, Study Finds Veggie Compound May Help Control NAFLD, Study Finds 8 Supplements for Detox and LiverJoshua Lambert, Associated Professor of Food Science at Penn State, explained the significance of the results in a press release: “By examining the livers of these mice after the study concluded and by screening their feces during the research, we saw that the mice that consumed green tea extract and exercised actually were processing nutrients differently—their bodies were handling food differently. We think the polyphenols in green tea interact with digestive enzymes secreted in the small intestine and partially inhibit the breakdown of carbohydrates, fat, and protein in food. So if a mouse doesn’t digest the fat in its diet, that fat and the calories associated with it pass through the mouse’s digestive system, and a certain amount of it ends up coming out in its feces.”
Nor is that all: Mice treated with both green tea extract and exercise had higher expression of genes related to the formation of new mitochondria. Lambert said in the release that this expression provides markers that will help researchers understand the mechanism by which green tea polyphenols and exercise might work together to mitigate fatty liver deposits.
However, Lambert urges caution: No human trials have assessed the benefits and risks of combining green tea with exercise. “I believe people should engage in more physical activity, and replacing high-calorie beverages with decaffeinated, diet green tea—which has no calories—is a smart move,” he said. “Combining the two might have health benefits for people, but we don’t have the clinical data yet.”