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Human study: weight loss slightly faster with green tea

A green tea-based soft drink helps fat people to lose weight a tiny bit more quickly, write researchers from the Kao Corporation in the Journal of Nutrition. Green tea accelerates weight loss in the abdominal area in particular.

The researchers gave 65 overweight people half a litre daily of a soft drink based on green tea. The slightly fewer people in the control group were given a soft drink that tasted the same. The test subjects did a moderate cardio work out at a gym three times a week, under supervision.

The product contained 40 mg of caffeine. The placebo drink also contained the same amount of caffeine. The green tea drink contained a total of 625 mg of catechins. An average cup of hot green tea contains about a hundred milligrams of catechins, but strong tea can contain up to one hundred and fifty milligrams.

The researchers monitored the weight loss of the test subjects over a period of twelve weeks. The results are shown below.

Human study: weight loss slightly faster with green tea

The control group lost about one kilogram of bodyweight; the green tea group lost a little over two kilograms. The difference was not quite statistically significant.

What was significant was the effect on the total abdominal fat area and the abdominal subcutaneous fat area. The other effects shown in the figure below were not significant.

Human study: weight loss slightly faster with green tea

The figures look convincing, but they are also a little misleading. A quick glance suggests that your waist area gets smaller as a result of drinking green tea, but if you read the article this turns out not to be the case. "Changes in waist circumference did not differ significantly (data not shown)", the researchers add in a none-too prominent sentence.

This is not the first study of its kind published by Kao one full of promise, but which ultimately contains few hard results. The company looks like it's following in the footsteps of Coca-Cola, which has managed to get studies published in scientific journals on the slimming effect of Enviga, a product also based on green tea.

The problems with the product tested is not that green tea doesn't work. Green tea does work. The problem is that you need a lot of it, and even then the effect is modest. An effective slimming stack based on green tea is 300 mg EGCG and 300 mg caffeine per day. EGCG is the most effective substance in green tea. The Kao product contains 214 mg of EGCG.

J Nutr. 2009 Feb;139(2):264-70.

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