Green tea extract effective for weight loss at low doses

By Stephen Daniells

- Last updated on GMT

Related tags Green tea Caffeine

Daily supplements of a purified extract of green tea may increase energy expenditure and help men beat the bulge, say results from a new human study.

A low dose of epigallocatechin gallate (EGCG) from green tea was found to increase fat oxidation by 33 per cent, according to findings published in the European Journal of Clinical Nutrition​.

“This pilot study provides for the first time evidence that a single green tea catechin, EGCG, can increase fat oxidation in obese men, at least within 2 h after meal intake. Within this postprandial phase, EGCG is equipotent with caffeine with regard to fat oxidation,”​ wrote the authors, led by Frank Thielecke from DSM Nutritional Products.

Growing waistlines, growing market

With the World Health Organization estimating that by 2015, there will be more than 1.5 billion overweight consumers, incurring health costs beyond $117 billion per year in the US alone, the opportunities for a scientifically-substantiated weight management food product are impressive.

Green tea has been studied extensively for its potential in the weight management category, with the compound epigallocatechin gallate (EGCG) highlighted as a key component.

Three mechanisms have been proposed: EGCG could increase energy metabolism and fatty acid oxidation; inhibit fat cell development (apidogenesis); and/or reduce lipid absorption and increase fat excretion.

It has also been reported that caffeine must also be present as, for EGCG to aid weight loss, a stimulated nervous system is needed.

The new research, performed in collaboration with scientists from Universitary Medicine Berlin, supports the link between caffeine and EGCG, but also found that the compounds produce similar effects. A daily dose of 300 mg of EGCG was associated with a 33 per cent increase in fat oxidation, while a daily dose of 200 mg caffeine was linked to a 34.5 per cent increase. When male subjects were given a combination of EGCG (300 mg) and caffeine (200 mg), fat oxidation increased by almost 50 per cent, added the researchers.

The EGCG used in the study was DSM's Teavigo ingredient, with 94 per cent EGCG purity.

Study details

Thielecke and his co-workers recruited ten healthy overweight and obese men (average BMI of 31.3 kg/m2) to participate in the randomized, placebo-controlled, double-blind crossover trial. The men were randomly assigned them to one of five groups: Placebo, low-dose EGCG (300 mg), high-dose EGCG (600 mg), caffeine (200 mg), or EGCG plus caffeine (300 mg/200 mg). The men took the supplements for three days, then seven days of washout, and cross-over to another group. At the end of the study, all the men had participated in each group.

Results showed that during two hours after a meal, the low-dose EGCG supplementation was associated with a 33 per cent increase in fat oxidation. The high-dose EGCG supplementation produced a non-significant 20 per cent increase, compared to placebo. Caffeine alone was associated with a 34.5 per cent increase, compared with placebo, while the combined EGCG/ /caffeine supplement boosted fat oxidation by 49 per cent. “There is no synergism of low EGCG and 200mg caffeine,” ​stated the researchers.

Commenting on the difference between high and low dose EGCG, the researchers noted that the lower dose may be optimal for affecting energy expenditure and higher doses do not provide any additional effects.

The results obtained for the combination of EGCG and caffeine may be related to the amount of time the compounds remain in the blood, with the so-called half-life of EGCG reprted to be about two hours while caffeine has a half-life of about four hours. “Therefore, EGCG affects obviously the early, whereas caffeine affects both early and late postprandial fat oxidation,”​ added Thielecke and his co-workers.

Support from other science

A recent review from researchers at Pennsylvania State University concluded that the science supporting the weight management potential of green tea and its extracts was (Journal of Nutrition​, doi: 10.3945/jn.109.115972).

Dr Josh Lambert, assistant professor in the Department of Food Science at Penn State told that laboratory studies and small-scale human intervention studies “indicate that consumption of tea might promote weight loss, help maintain body weight following weight loss, and prevent the development of some diseases associated with obesity such as diabetes and fatty liver disease”.

“The effective doses seem to be 3 to 10 cups of green tea per day,”​ he added.

Weight management potential

The market for food, beverage and supplement weight management products is already valued at $3.64bn (2009 figures) in the US, according to Euromonitor. In Western Europe, the market was worth $1.3bn in 2009.

Source: European Journal of Clinical Nutrition
Published online ahead of print, doi: 10.1038/ejcn.2010.47
“Epigallocatechin-3-gallate and postprandial fat oxidation in overweight/obese male volunteers: a pilot study”
Authors: F. Thielecke, G. Rahn, J. Böhnke, F. Adams, A.L. Birkenfeld, J. Jordan, M. Boschmann

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