Green tea leaf extract is a natural ingredient obtained from a plant called Camellia sinensis. It’s the same plant used for the green tea people all over the world enjoy on a daily basis. Both the leaves, the stem and the buds of this plant can be used for beverage and medicinal purposes, but it is the leaves that are most often used in high quality diet supplements.

To prepare green tea leaf extract, the leaves need to be steamed and pan-fried before being dried out. This process differs from the process of making other types of tea such as black tea or oolong, which require a certain amount of fermentation. That said, this method also makes it possible to keep polyphenols – important chemicals that produce certain wanted benefits – intact.

In fact, it is the polyphenols that are most often credited for the many advantages of green tea leaf extract consumption. They help to prevent swelling and inflammation, they reduce joint degeneration, they protect the cartilage between the bones and offer a range of support to dieters focused on weight management. Science has yet to determine exactly how this ingredient produces its many benefits, despite the number of studies that have linked its use to advantageous functions in the body.

Beyond the polyphenols, green tea also contains caffeine – usually between 2 percent and 4 percent. This naturally occurring chemical is known to boost alertness and stimulate the heart, muscles and central nervous system. This may help to increase the metabolic rate and some people who use it experience appetite suppression.

The antioxidants in green tea help to provide the heart and blood vessels with protection while they also help to boost the immune system and it might help to reduce the risk of certain cancers if taken regularly.

A study published in the American Journal of Clinical Nutrition showed that when study participants took green tea leaf extract, their metabolisms increased – that is, their 24 hour energy expenditure was higher than the placebo group. This implies that when taking this substance, the body burns more fuel (typically in the form of calories from food or stored body fat) than it would without this ingredient.

Another study, this one published in the Phytomedicine journal, showed that taking green tea extract stimulates thermogenesis and inhibits lipase in the pancreatic and gastric systems. This suggests that the body temperature rises, thereby increasing the amount of fuel it needs to function (calories or fat), while the enzyme it uses to digest fat reduces, so more dietary fat passes through the body undigested.

A meta analysis published in the International Journal of Obesity found that the catechins or the EGCG-caffeine combination have a small but measurable impact on both weight loss and weight maintenance.

The Obesity journal published another study in which it was found that women who take green tea extract can experience increased thermogenesis and fat oxidation as well as leptin suppression. The combination of green tea with caffeine was particularly potent among study participants who didn’t habitually use caffeinated products prior to the study.

* Abdul G Dulloo, Claudette Duret, Dorothée Rohrer, Lucien Girardier, Nouri Mensi, Marc Fathi, Philippe Chantre, and Jacques Vandermander. “Efficacy of a green tea extract rich in catechin polyphenols and caffeine in increasing 24-h energy expenditure and fat oxidation in humans”. American Journal of Clinical Nutrition. December 1999. Volume 70, Issue 6, pages 1040-1045. http://ajcn.nutrition.org/content/70/6/1040.short

**P. Chantre, D. Lairon. “Recent findings of green tea extract AR25 (Exolise) and its activity for the treatment of obesity”. Phytomedicine. 2002 Volume 9, Issue 1, pages 3-8.

*** Hursel, R., Viechtbauer, W., Westerterp-plantenga, M S. “The effects of green tea on weight loss and weight maintenance: a meta-analysis”. International Journal of Obesity. 2009 Volume 33, Issue 9, pages 956-61. https://search.proquest.com/openview/dd94b48b5f030f77342e8392f411964a/1?pq-origsite=gscholar&cbl=38864

**** Westerterp-Plantenga, M.S., Lejeune, M.P.G.M., Kovacs E.M.R. “Body Weight Loss and Weight Maintenance in Relation to Habitual Caffeine Intake and Green Tea Supplementation”. Obesity. 2005 Volume 13, Issue 7, pages 1195-1204. http://onlinelibrary.wiley.com/doi/10.1038/oby.2005.142/full