Studies Show ... .
By Robert Nordstrom, Contributor

Anyone who has spent time browsing “tea” on the Internet has likely come across the mountains of material promoting the weight loss benefits of pills and liquids containing extracts or ingredients of tea, particularly green and oolong.
Some of these sites present their information in a research-like format. But as you move through this so-called “research” – generously sprinkled with links connected to words such as “weight loss,” “diet” and “health” – you’re likely to find that the links take you to weight loss products. On one site I visited, a link connected to the word “diet” took me to a sneak preview of an upcoming episode of the TV program “Lost.” 

Does tea affect weight loss? Various studies on tea’s relationship to weight loss are promising, but virtually all of them offer the caveat that better and larger clinical studies are needed.

In this article, WTN looks at evidence supporting the beneficial effects of green and oolong teas on weight loss. In a subsequent article, we will look at the weight loss claims of products containing tea ingredients and extracts.

Oolong vs. Caffeinated Water
One frequently cited study, conducted by physiologist William Rumpler of the USDA’s Agricultural Research Service (published in the December 2001 issue of the Journal of Nutrition), found that energy expenditure (EE) increased by 2.9 percent among men ages 25 to 60 years old who drank full-strength oolong tea and 3.4 percent among men who received caffeinated water.

Additionally, however, fat oxidation was significantly higher (12 percent) among subjects who consumed the full-strength tea rather than the caffeinated water.
The researchers concluded that “an unclear compound in oolong tea, other than the caffeine, increases fat oxidation and may help to promote weight loss.” They added that more large-scale investigations were needed to clarify the relationship.

Green vs. Oolong
T. Komatsu, of the University of Tokushima School of Medicine in Japan, studied the effects of oolong tea on EE compared with the effects of green tea in eleven Japanese women. Results (published in the 2003 issue of the Journal of Medical Investigation) indicated that EE increased by 10 percent among those who consumed oolong tea and 4 percent among those who consumed green tea.
Komatsu concluded that oolong tea – which contained approximately half the caffeine and epigallocatechin gallate (or EGCG, an antioxidant) contained in green tea, but twice the amount of polymerized polyphenols – increases EE (a critical factor in weight loss) through its polymerized polyphenols.

Swen Wolfram et al. took issue with Komatsu’s claim that oolong burns “2.5 times more calories than green tea” in their 2006 article, “Anti-obesity effects of green tea” (published in the February 2006 issue of Molecular Nutrition & Food Research). Wolfram said that Komatsu’s study had methodological deficiencies, including the small sample size, test duration and gas analysis methods. Also, the teas consumed by participants were not directly comparable.

Complicating matters further, in an article published January of 2001 in the Journal of Nutritional Biochemistry, Ming-Hua Yang et al. found that green tea burned more fat than oolong tea and black tea in rats with high levels of fat in their blood. They concluded that fat metabolism is greater with green tea consumption than it is with oolong or black tea.

EGCG and Type-2 Diabetes
In a study of the effects of green tea extract on diabetic rodents, published in the October 2006 issue of the Journal of Nutrition, a team of researchers led by Wolfram found that EGCG exerted “potent anti-diabetic activity.” Wolfram further stated that “supplementation with EGCG could potentially improve glucose tolerance in humans with type-2 diabetes mellitus.”

Again, they offered the caveat that this hypothesis needs further investigation in randomized placebo-controlled trials.

What It All Means
So, does tea help you lose weight? The best answer for now is, “Maybe.”
While the verdict is out on the weight-loss benefits of tea, per se, research does make interesting observations on the effects of tea on fat oxidation, energy expenditure and glucose tolerance.