EGCG stands for epigallocatechin-3-gallate. It is the main antioxidant in tea, said to be more than 100 times more powerful than vitamin C. There is more of it in white and green tea than in black tea.
EGCG is responsible for the cancer-protective effect observed with green tea. It also appears to protect the heart and arteries from oxidative damage and, applied topically, may protect the skin from the damaging effects of ultraviolet radiation and reverse precancerous skin changes. To get an optimal dose of EGCG, you should drink about four cups of green tea daily.
Despite its many beneficial effects, I know of no good evidence to suggest that EGCG promotes weight loss. A study at the University of Chicago did show that rats injected with EGCG lost their appetites and ate up to 60 percent less than normal, but there was no effect on the rats' appetites when they were given EGCG orally. The researchers who conducted the study speculated that long-term oral administration of EGCG might have the same effect on appetite as the injections but cautioned that humans would have to drink green tea constantly to get the results seen in the animal study. Furthermore, the EGCG injections caused hormonal changes in the rats that could have negative effects on health if they occurred in humans.
The research most often cited in advertisements for weight-loss products containing EGCG include a very small study (only 10 men took part) published in the December 1999 issue of the American Journal of Clinical Nutrition. It showed that 90 mg of EGCG plus 50 mg of caffeine boosted metabolism. Another study mentioned in the ads was published in the January 1, 2002 issue of Phytomedicine and suggested that taking EGCG supplements might result in a weight loss of about 2.5 pounds per month. Emphasis is on "might." I'd suggest drinking green tea for its proven health benefits and forget about EGCG for losing weight. Instead, concentrate on eating less and exercising more.
Andrew Weil, M.D.