Green Tea and Weight Loss

Long revered for its ability to increase blood flow, neutralize toxins, improve resistance to disease, and enhance urine flow, green tea has caught the attention of many consumers for its weight-reducing power. And for good reason-the science behind green tea is confirming what the Chinese have known for more than 4,000 years.

How It Works
If there's a single, primary mechanism behind green tea's effect on weight loss, researchers haven't yet agreed on it. For example, green tea appears to act on several tissues (fat, muscle, liver, intestines) and, as a result, can increase the rate at which we burn calories, preferentially increase fat oxidation, increase glucose uptake in muscle, and decrease glucose uptake in fat. In addition, scientists have shown that green tea slightly reduces fat and carbohydrate absorption by inhibiting gastric and pancreatic lipases as well as the activity of amylase and sucrase (different types of enzymes). Finally, molecular biologists are now uncovering evidence that green tea may also act on key genes to inhibit increases in fat cell size and number. From a scientific perspective, this myriad of potential mechanisms makes green tea all the more intriguing.

In the real world, green tea is usually consumed as a powdered extract or as a beverage. Studies have uncovered a unique interaction between caffeine and green tea's other components that makes them an effective means of enhancing body composition. In a nutshell, caffeine inhibits an enzyme called phosphodiesterase, which normally breaks down molecules that enhance intracellular energy production. EGCG (the major component in green tea polyphenols) inhibits a different enzyme called COMT (catechol-O-methyl-transferase) that breaks down the "fight-or-flight" hormone noradrenalin, prolonging its thermogenic activity in the body. Thus when caffeine and EGCG are combined-bang!-both enzymes are inhibited and energy use is increased dramatically.

Recent Buzz
Swiss researchers recently published a review of the potential benefits of green tea and EGCG on weight loss. Based on the existing studies on humans, they concluded that green tea (either in beverage or capsule form) can promote weight loss over a period of 12 weeks. They also noted that, although green tea and EGCG appear to work synergistically with caffeine, subjects who typically consume less caffeine in their diet appear to respond better to the weight-reducing power of green tea, compared to those who consume high amounts of caffeine daily.

The Final Analysis
In my experience as a scientist, considering the risk-to-benefit ratio of substances that promote weight loss is paramount. This is where green tea shines. In contrast to most supplements promoted for weight loss, green tea appears very safe and effective. In fishermen's lingo, "This one's a keeper."

Tips for Promoting Weight Loss

• Think tortoise. When it comes to using green tea for weight loss, slow and steady wins the race. Unless you are dieting, don't expect to see significant weight loss before approximately 12 weeks of continuous use.
• Empty the tank. Take green tea between meals to improve its bioavailability and reduce the risk of its interfering with iron absorption.
• Don't forget diet and exercise. For maximum benefits on body composition and overall wellness, combine green tea ingestion with a healthy, calorie-reduced diet and regular physical activity.

"Anti-obesity effects of green tea: From bedside to bench" by S. Wolfram et al., Mol Nutr Food Res, 2006 "Bioavailability and antioxidant activity of tea flavanols after consumption of green tea, black tea, or a green tea extract supplement" by S. M. Henning et al., Am J Clin Nutr, 12/04 "Effects of dosing condition on the oral bioavailability of green tea catechins after single-dose administration of polyphenon E in healthy individuals" by H. H. Chow et al., Clin Cancer Res, 6/05 "Relationship among habitual tea consumption, percent body fat, and body fat distribution" by C. Wu et al., Obes Res, 9/03