Green tea and weight loss

 Green tea is the non-oxidized, non-fermented product made from the leaves of Camellia sinensis. Green tea is being touted as an easy solution to get rid of all the excess fat and slim down. But is it really a miracle worker?

The key to losing weight is increasing the energy expenditure and fat oxidation of the body. Drinking green tea achieves this exact thing: courtesy the catechins present in them. Catechins are the major constituents of green tea and are basically antioxidant molecules.

Energy homeostasis is regulated by the sympathetic nervous system (SNS). Norepinephrine, also known as noradrenaline, is a stimulant of SNS pathway. Norepinephrine can be broken down by the enzyme  catechol O-methyltransferase (COMT) The catechins inhibit the COMT enzyme thereby preventing the breakdown of norepinephrine. Norepinephrine in turn stimulates fat metabolizing enzymes leading to increased fat oxidation. It also upregulates the gene expression of the proteins involved in heat production during ATP generation, thus increasing the energy expenditure.  It also has a negative effect on insulin thereby reducing the glucose uptake in cells.  Also, green tea itself has no calories!

However, drinking green tea does not result in the same outcome for every individual. Research has found that Asians are more likely to be benefited by drinking green tea as compared to the Caucasians. This is because of the inherent genetic variability in the type of COMT enzyme that these 2 populations have. The Asians have a high activity COMT while the Caucasians have a low activity COMT. Therefore, inhibition of the COMT produces a more pronounced effect in the Asian population as compared to the Caucasians.

Reference:

http://www.nature.com/ijo/journal/v34/n4/full/ijo2009299a.html