There is some scientific evidence on the benefits of green tea for weight loss. A catechin (phytochemical compound) in green tea called epigallocatechin gallate (EGCG) has been found to have thermogenic properties and promotes fat oxidation. EGCG extract is also available as a dietary supplement.
Thermogenesis is the process by which the body promotes energy expenditure. All foods have some thermogenic effect as the body uses energy for processing food, but not all foods have the same thermogenic effect. Protein has the highest thermogenic effect, dietary fat has little thermogenic effect, and carbohydrates have medium thermogenic effect. By increasing thermogenesis, energy expenditure is increased and fat cells are then used as energy.
Green tea for weight loss shouldn’t be regarded as a single remedy; however it clearly helps with the reduction of fat tissue through the increased fat oxidation and thermogenesis that it promotes. This will improve the ratio of muscle tissue to fat, which in turn promotes an increased metabolism and additional burning of fat.
Green Tea for Weight Loss Study 1
A study in 10 healthy men, supplementing with a green tea extract (90 mg EGCG and 50 mg caffeine), 3 times daily, resulted in a significant increase in 24 hour energy expenditure. The study concluded that green tea possesses thermogenic properties and also promotes fat oxidation over and above that explained by the caffeine content by itself. These thermogenic properties of EGCG provide a small but significant benefit of green tea for weight loss.
Green Tea for Weight Loss Study 2
In another 12-week study of 60 obese people, supplementing their daily diets with green tea caused weight loss of 2.70, 5.10, and 3.3 kg during the 4th, 8th, and 12th weeks of the study, respectively. The study showed that the usefulness of green tea for weight loss in obese people was due to higher energy output as well as better fat oxidation.
Green Tea for Weight Loss Study 3
In another clinical trial, Japanese women and men with visceral fat-type obesity ingested a green tea extract that contained 583 mg of catechins (this was the catechin group) or 96 mg of catechins (this was the control group) each day. The participants were told to continue to stick to their normal dietary intake as well as usual physical activity. The group ingesting the green tea extract high in catechins experienced a reduction in body fat and LDL cholesterol, suggesting that the ingestion of such an extract contributes to a decrease in obesity and cardiovascular disease risks.
Green Tea for Weight Loss Study 4
The results of another 12-wk double-blind study also suggested that daily intake of green tea that contained 690 mg catechins can be useful in the prevention and treatment of obesity.
There is also evidence that EGCG activates AMP-activated protein kinase (AMPK). AMPK plays a key role in the regulation of carbohydrate and fat metabolism.
It’s vital to bear in mind that the catechin content of green tea differs very much depending on the area of cultivation and the processing techniques that have been used. Below is a chart with estimations of EGCG content in various types of green tea.
The infusion or brewing time is also a significant aspect in final catechin content. A brewing time of less than 5 minutes allows the withdrawal of only 20 % of the catechins that would normally be extracted after an infusion of 8-10 minutes.
A cup of Ti Kuon Yin tea brewed for 2 minutes provides 9mg polyphenols per cup. A cup of gyokuro tea brewed for 10 minutes provides 540mg polyphenols per cup.
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