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Food, Health, and Eco-news
Green Tea Weight Claim Gets a Clinical Boost
Clinical trial finds that caffeine and green tea antioxidants yield a similar fat-burning boost, and that the combination of both produced a 49 percent increase
by Craig Weatherby

The World Health Organization estimates that there will be more than 1.5 billion overweight people by 2015.

And it's estimated that the negative health effects of expanding waistlines will cost America $117 billion annually.

Key Points
  • The main antioxidant in green tea (EGCG) rivaled caffeine's fat-burning effects in a small, well-designed clinical trial.
  • Separately, EGCG and caffeine boosted fat-burning by one-third.
  • Together, EGCG and caffeine boosted fat-burning by almost 50 percent.
  • Two cups of tea contain the effective dose of EGCG, and about one-third of the caffeine dose.
  • Neither EGCG nor caffeine increased calorie-burning, but both bring metabolic benefits associated with long term weight control and diabetes deterrence.
The only diet pill approved by the FDA in more than 20 years—the famous fiasco known as Redux—proved downright dangerous and was quickly withdrawn.

So, attention has turned to natural constituents of foods and herbs, with caffeine and its various sources—coffee, guarana, kola nut, and yerba maté—leading the pack.

Caffeine can aid weight control, partly by suppressing appetite but mostly by boosting the fat-burning process called thermogenesis (heat-generation).

But many people find any amount of caffeine—much less the 100mg dose in a cup of coffee—over-stimulating and/or insomnia-inducing.

Hope for green tea antioxidants as caffeine substitutes
As it turns out, the catechin-class antioxidants in green teaespecially the most abundant one, called EGCGenhance some of the same fat-burning processes stimulated by caffeine.

In fact, it appears that EGCG and certain of its companion catechins may aid weight control in several ways: they seem to raise metabolism, increase fat burning, discourage development of fat cells, reduce fat absorption, and increase fat excretion.

Those findings have raised hopes that caffeine-free teaor caffeine-free green tea extractsmight provide a jitter-free weight management ally.

However, there's also some evidence that EGCG aids weight loss best when the nervous system has been stimulated by compounds like caffeine.

That belief was bolstered earlier this year when pharmacists from the University of Connecticut (UCONN) published a review of 15 prior clinical trials that tested the fat-burning and weight control effects of various green tea catechins (GTCs).

In short, the combined results of those trials indicate that caffeine alone exerts modest weight control effects, that GTCs alone do little, and that the combination of GTCs and caffeine found in whole green tea works a bit better than caffeine alone.

As the UCONN team wrote, “The administration of GTCs with caffeine is associated with statistically significant reductions in BMI, body weight, and WC [waist circumference] Current data do not suggest that GTCs alone positively alter [these] anthropometric measurements” (Phung OJ et al. 2010).

But last year, Danish researchers noted that the wide range of results obtained in different clinical trials could be due to variations in the composition of various green tea extracts: “…higher short-term [fat-burning] effects reported in the literature may reflect variations in green tea extracts, added caffeine, or synergies with physical activity” (Gregersen NT et al. 2009).

Now, the results of a Swiss clinical trial support the idea that green tea's catechin-class antioxidants do more than increase caffeine's impacts... they may actually rival the fat-burning effects of caffeine.

Green tea antioxidant may rival caffeine for fat burning
The results of a Swiss-German clinical trial suggest that a modest amount of EGCG from green tea can increase fat burning (oxidation) by one-third (33 percent).

Importantly, this was about as much as fat-burning as was produced by a modest dose of caffeine.

And they showed that a combination of EGCG and caffeine raised fat-burning by a whopping 49 percent (Thielecke F et al. 2010).

Accordingly, the researchers viewed their results as a breakthrough: 

“This pilot study provides the first evidence that a single green tea catechin, EGCG, can increase fat oxidation [burning] in obese men, at least within 2 hours after meal intake… [which means that] EGCG is equipotent with [equals] caffeine with regard to fat oxidation.”

The Swiss-German team recruited 10 healthy overweight and obese men to participate in a well-designed clinical trial (randomized, placebo-controlled, double-blind, and crossover).

The participants were randomly assigned to one of five groups:

Placebo pill
Low-dose EGCG (300? mg)
High-dose EGCG (600? mg)
Caffeine (200? mg)
EGCG (300? mg) plus caffeine (200? mg)

The men took the supplements for three days, followed by seven days of “washout” (no supplements), and then crossed over to another group. At the end of the study, all the men had participated in each group.

None of the groups showed any increase in the number of calories burned.

But that is not the only measure of success for a weight control prospect, because over time, burning of stored fat can result in weight loss.

And the new trial confirmed the ability of both caffeine and EGCG to raise fat-burning levels.

Compared to placebo pills, each of the four test regimens produced different increases in fat-burning during the two hours following a meal:

Placebo pills produced no increase.

Low-dose EGCG (300? mg) produced a 33 percent increase.
High-dose EGCG (600? mg) produced a statistically non-significant 20 percent increase.
Caffeine alone (200? mg) produced a 34.5 percent increase.
Combined EGCG/caffeine (300? mg/200 mg) produced a 49 percent increase.

The researchers noted that the lower EGCG dose may be optimal, since the higher dose actually produced lesser effects.

The superior results seen with the combination of EGCG and caffeine seem to affirm the notion that green tea catechins do a better job of boosting fat-burning in the presence of a stimulant like caffeine.

Does tea contain enough EGCG and caffeine?
The question arises of whether a cup or two of green tea contains amounts of EGCG and caffeine comparable to the levels that produced fat-burning boost in this trial.

A single cup of green tea contains about 30mg of caffeine, and a British study found that the average cup contains about 135mg of catechins, with EGCG making up most of that (Khokhar S et al. 2002).

In other words, it appears that two cups of green tea provide about 270mg of catechins and 60mg of caffeine.

Thus two cups would provide an EGCG dose comparable to the amount that produced optimal fat-burning effects in the new clinical trial, but considerably less caffeine.

Of course, we cannot know whether it takes the 200mg of caffeine used in the trial, or whether 60mg is enough to produce the synergy needed for optimal fat-burning outcome.

And none of this implies that green tea is a wonder weight-loss drug.

Rather, it may simply be a helpful, relaxing ally in the battle of the bulge.

For more on the weight control effects of certain food factors see “Food Allies in the Weight War: Spices, Tea, and Fish,” “Exercise + Omega-3s = Perfect Weight Loss Pair,” and “Eat Fish, Lose Weight, Feel Better,” and “Hot Factor in Chilies May Hinder Fat Build Up.

  • Basu A, Lucas EA. Mechanisms and effects of green tea on cardiovascular health. Nutr Rev. 2007 Aug;65(8 Pt 1):361-75. Review.
  • Boschmann M, Thielecke F. The effects of epigallocatechin-3-gallate on thermogenesis and fat oxidation in obese men: a pilot study. J Am Coll Nutr. 2007 Aug;26(4):389S-395S.
  • Friedman M, Levin CE, Lee SU, Kozukue N. Stability of green tea catechins in commercial tea leaves during storage for 6 months. J Food Sci. 2009 Mar;74(2):H47-51
  • Gregersen NT, Bitz C, Krog-Mikkelsen I, Hels O, Kovacs EM, Rycroft JA, Frandsen E, Mela DJ, Astrup A. Effect of moderate intakes of different tea catechins and caffeine on acute measures of energy metabolism under sedentary conditions. Br J Nutr. 2009 Oct;102(8):1187-94. Epub 2009 May 18.
  • Khokhar S, Magnusdottir SG. Total phenol, catechin, and caffeine contents of teas commonly consumed in the United kingdom. J Agric Food Chem. 2002 Jan 30;50(3):565-70.
  • Phung OJ, Baker WL, Matthews LJ, Lanosa M, Thorne A, Coleman CI. Effect of green tea catechins with or without caffeine on anthropometric measures: a systematic review and meta-analysis. Am J Clin Nutr. 2010 Jan;91(1):73-81. Epub 2009 Nov 11. Review.
  • Sarma DN, Barrett ML, Chavez ML, Gardiner P, Ko R, Mahady GB, Marles RJ, Pellicore LS, Giancaspro GI, Low Dog T. Safety of green tea extracts : a systematic review by the US Pharmacopeia. Drug Saf. 2008;31(6):469-84. Review.
  • Thielecke F, Boschmann M. The potential role of green tea catechins in the prevention of the metabolic syndrome - a review. Phytochemistry. 2009 Jan;70(1):11-24. Epub 2009 Jan 13. Review.
  • Thielecke F, Rahn G, Böhnke J, Adams F, Birkenfeld AL, Jordan J, Boschmann M. Epigallocatechin-3-gallate and postprandial fat oxidation in overweight/obese male volunteers: a pilot study. Eur J Clin Nutr. 2010 Apr 7. [Epub ahead of print]
  • Westerterp-Plantenga MS, Lejeune MP, Kovacs EM. Body weight loss and weight maintenance in relation to habitual caffeine intake and green tea supplementation. Obes Res. 2005 Jul;13(7):1195-204.
  • Westerterp-Plantenga MS. Green tea catechins, caffeine and body-weight regulation. Physiol Behav. 2010 Apr 26;100(1):42-6. Epub 2010 Feb 13.


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