“Promising” is a word often used in discussions about tea’s ability to boost your metabolism and help you lose weight and burn fat.
But don’t hold your breath waiting for the proof of that promise. Although there’s certainly some evidence, and lots of hype, that the catechins and/or epigallocatechin gallate (EGCG) in green tea promotes better weight management, the number of human studies in this field is still quite limited.
Rick Hursel, a human biologist at Maastricht University Medical Centre in the Netherlands, is one of the researchers who has studied the effects of green tea on metabolism.
He conducted a meta-analysis of 11 articles on the subject and concluded that “catechins or an epigallocatechin gallate (EGCG)-caffeine mixture have a small positive effect on weight loss and weight management.”
“We’ve shown that green tea is able to increase your energy expenditure — so the amount of calories you burn — and also to increase the amount of fat you are burning,” Hursel said in an interview with National Public Radio. But NPR noted that the weight loss effect in the study was small — and perhaps fleeting.
Another study, published by the Cochrane Review, found that green tea “appear to induce a small, statistically non-significant weight loss in overweight or obese adults. Because the amount of weight loss is small, it is not likely to be clinically important.” That study found that drinking green tea had no significant effect on the maintenance of weight loss.
Chinese Medicine, the official journal of the International Society for Chinese Medicine, published an overview of the benefits of green tea several years ago. The journal concluded that “tea catechins, especially EGCG, appear to have anti-obesity effects.”
The authors cited promising in vitro and animal studies and looked at human studies on using green tea catechins to treat metabolic syndrome, the name given for a group of risk factors, including abdominal obesity, that increase the chance of developing serious health problems. They found that the long-term consumption of tea catechins could be beneficial against high-fat diet-induced obesity and type II diabetes and could reduce the risk of coronary disease.
“Recent data from human studies indicate that the consumption of green tea and green tea extracts may help reduce body weight, mainly body fat, by increasing postprandial thermogenesis and fat oxidation,” according to the journal article.
The article cited a small study – just six overweight men were given 300 mg EGCG per day for two days – that suggested that EGCG alone has the potential to increase fat oxidation in men and may thereby contribute to the anti-obesity effects of green tea.
Frank Thielecke and Michael Boschmann also looked at metabolic syndrome.
“The majority of human epidemiological and intervention studies demonstrate beneficial effects of green tea or green tea extracts, rich in EGCG on weight management, glucose control and cardiovascular risk factors,” they wrote in the journal Phytochemistry.
But, they said, “the optimal dose has not yet been established. The current body of evidence in humans warrants further attention. In particular, well-controlled long-term human studies would help to fully understand the protective effects of green tea catechins” on metabolic syndrome.