There's good news for dieters: green tea appears to speed up calorie burning, including fat calorie burning. The green tea extract may play a role in the control of body composition. Researchers studied the effects of green tea on 10 healthy young men, average age 25, who ranged from lean to mildly overweight. For 6 weeks, the men took two capsules at each meal: green tea extract plus 50 milligrams of caffeine; 50 milligrams of caffeine; or a placebo (inactive capsule).
The study participants were on a weight maintenance diet of about 13% protein, 40% fat, and 47% carbohydrates, a "typical Western diet." Three times during the study, the men spent 24 hours in a special room where the investigators measured their respiration and energy expenditure. Energy expenditure, the number of calories used during a 24-hour period, was higher for men taking green tea extract than for those taking caffeine or placebo. They also found evidence that men taking the green tea extract used more fat calories than those taking the placebo.
There was no difference between the caffeine users and the placebo users in terms of either overall calorie burning or fat calorie burning. The researchers therefore conclude that the increased calorie burning in the green tea group cannot be explained by caffeine intake alone. The investigators suggest that the caffeine interacted with natural substances in green tea called flavonoids to alter the body's use of norepinephrine, a chemical transmitter in the nervous system, and increase the rate of calorie burning. The researchers point out that, unlike some diet products, green tea does not contain high doses of caffeine, and it did not affect the heart rate in the study participants.
American Journal of Clinical Nutrition November 1999;70:1040_1045.
COMMENT: I believe green tea should still be considered a drug and it should not be considered a ?cure? for weight loss. However, when one is exercising vigorously for one hour per day (see below) and has a low grain diet see Read This First), then it may be a helpful short-term aid to facilitate weight loss. Green tea has powerful antioxidants, which also may provide protection against coronary artery disease. However, if one reviews the next article it appears that oolong tea may be the preferred choice.