As of Friday, January 25, 2013
There is recent evidence that a chemical found in ordinary green tea, epigallocatechin gallate (EGCG), may offer a bit of weight loss magic.
Unlike black teas, which are made with fermented leaves, green tea (camellia sinensis) is produced by steaming fresh leaves. This production process results in higher content of polyphenols like EGCG, which is a flavonol. Black tea has 3 to 10 percent polyphenols, while green tea has 30 to 40 percent.
Because of its high polyphenols, green tea is ascribed all kinds of health benefits, from normalizing blood pressure to lowering cancer risk. Future research will likely clarify whether or not any of the phenols have disease-fighting effects.
The proposed mechanism for green tea’s calorie-burning properties lies in the ability of EGCG to increase thermogenesis, or heat production, by influencing enzymes in the metabolic process. This means that EGCG seems to increase the amount of calories burned throughout the day for all activities, from digesting food to climbing stairs to typing.
Other food components, like caffeine or capsaicin (in hot peppers) can boost calorie burning, but EGCG has a stronger effect. However, the effect is not likely to melt pounds off overnight.
A variety of studies on the effect of EGCG on weight and metabolism have been published. Most of them have encouraging results. In one study, energy expenditure was compared in men who were given green tea extract versus caffeine or plain water. The green tea extract caused a 4 percent boost in metabolism. The amount of extract given was approximately the amount reported to be in a cup of green tea.
People who enjoy drinking green tea and who are watching their weight might already be getting a small boost in metabolism. If you want to try adding green tea to your diet plan, keep in mind it also contains caffeine, albeit less than coffee.
Also, the polyphenols in green tea are biologically active, and may interfere with medications you take. A pharmacist or physician can advise on this issue.
As research into the effects of EGCG continues and its usefulness as a metabolism-booster is clarified, purified forms may become available. For now, enjoy a cup of green tea, but don’t expect weight loss miracles.
Donna Feldman, M.S., R.D., writes online health columns for The Diet Channel.