Green tea's rich cultural history dates back many centuries, with botanical evidence suggesting that the herbal drink first became popular in India and China. Green tea has also endured as a potential aid in dieting, with modern science confirming that this traditional beverage may help as part of a weight loss regime.
Green Tea
The University of Maryland Medical Center reports that green tea stands out as the world's favorite drink, second only to water in terms of popularity. Brewed from unfermented leaves of the camelia sinensis plant, green tea maintains a different nutritional profile to that found in regular black tea. The University notes that, because of the lack of processing after picking, green tea leaves contain higher levels of antioxidants. It identifies the catechins as especially important in green tea's weight loss effects.
Nutritional Profile
Because of the lack of processing after picking, green tea leaves contain higher levels of antioxidants. The University of Maryland Medical Center explains that tea leaves also contain a wealth of carotenoids and chlorophyll, which gives the drink its characteristic hue. The center identifies the catechins as especially important in green tea's weight loss effects.
Catechin Content
Green tea remains the most concentration source of catechins. David Tolson, a nutritional researcher and contributor to "Iron Magazine," reports that these compounds make up around 10 percent of the weight of tea leaves. He explains that these plant chemicals, a sub-group of polyphenols, come in six different forms. Of these, epigallocatechin-gallate stands out as the most powerful and has received most scientific scrutiny.
Diet Aid
The primary mechanism through which the catechins affect weight loss appears to be the way that they inhibit an enzyme called COMT. This enzyme normally breaks down noradrenaline, a peptide hormone that binds to receptors in the central nervous system and stimulate thermogenesis. By increasing the availability of noradrenaline, consuming green tea can increase the heat production and fat burning that occurs during this process. Tolson also notes that catechins appears to reduce the intestinal absorption of fat, which may also contribute to its weight loss effect.
Effectiveness
Scientists from Maastricht University in the Netherlands looked into the fat-burning properties of green tea in a 2005 experiment. Starting with 76 volunteers, they measured their bodyweight, waist size and total energy expenditure before dividing them into two groups. One group acted as the controls while the other received a green tea extract. They found that the green tea group lost more weight, reduced their average waist circumference and burned more energy at rest than those who received placebos. The results were featured in the "Obesity Research" journal of July 2005.
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