Green Tea and Weight Loss: The Latest Research
Does green tea burn fat and boost metabolism? Read on to find out.
Green tea, originally from China, is popular throughout Asia and, more recently, the United States. It is made solely from the leaves of the flowering plant known as Camellia sinensis. In fact, black, oolong and green tea are all derived from the leaves of this plant, which grows to the size of a shrub. The leaves of black tea are fully fermented; those of oolong tea are partially fermented, and the leaves of green tea are unfermented. Today, Camellia sinensis grows in Africa and the Middle East as well as throughout Asia. Green tea is so popular due, in large part, to its well researched health benefits. There are many varieties of green tea that differ according to factors such as horticulture, growing conditions and harvesting time.
Green tea is high in antioxidants, polyphenols, catechins and other health promoting compounds. Results of dozens of research studies suggest that green tea may reduce the risk of cardiovascular disease, cancer, kidney stones and protect teeth from decay. In addition, the catechins in green tea, particularly in combination with caffeine, stimulate fat oxidation in humans.
What is the latest research on green tea and fat loss?
One of the most promising publications was a meta-analysis of many research studies on green tea and weight loss, published in the International Journal of Obesity, September 2009. According to this article, based upon the pooled results of 11 research studies, the catechins particularly that present in green tea, epigallocatechin gallate (EGCG), decreased body weight and promoted weight maintenance after a period of weight loss. This effect was independent of caffeine intake as well as ethnicity. Thus, catechins alone or an epigallocatechin gallate (EGCG)-caffeine mixture has a small but positive effect on weight loss and maintenance after loss.
Another review, published in the Journal of Nutritional Biochemistry in January 2011 examined the results from a handful of randomized, controlled intervention trials. These trials have consistently shown that consuming 270 milligrams (mg) to 1200 mg of green tea catechins (GTC) may reduce body weight and fat (enhance fat burning).
How does it work?
There are several possible mechanisms of how GTC alters body composition and weight. The most widely believed mechanism is that the various tea catechins influence sympathetic nervous system (SNS) activity. This activity results in an increase in total energy expenditure (EE, calories burned) and fat oxidation. Caffeine is naturally present in green tea and is also known to influence sympathetic nervous system activity. Together, these substances work in synergy and have a greater effect. Other proposed theories of how GTC alters body composition/weight include GTC modifying/altering appetite and/or an up-regulation of enzymes (in the liver) involved in fat oxidation.
How much GTC is necessary to produce a desired effect?
According to research conducted in 1999, capsules containing 375 mg of GTCs, specifically 270 mg of EGCG and 150 mg of caffeine, increased 24-hour energy expenditure by about 4%. Since thermogenesis or the heat produced from metabolic reactions, accounts for 8 to 10% of the average individual’s caloric expenditure, a 4% increase, in a sedentary male, might burn an additional 300+ calories. One 7-oz cup of steeped green tea provides, on average, 20-35 mg of EGCG and about 20 mg of caffeine. While there are GTC supplements available, with concentrated amounts of EGCG and caffeine, drinking green tea alone is safe and offers other health benefits. To lose 1 lb of body weight in one week, you must expend an additional 3,500 calories. While adding green tea to your regime will likely not increase energy expenditure to a significant enough level and/or cause fat to ‘melt’ off your body, it certainly cannot hurt. The Asians have been drinking an average of three cups of tea, including green tea, for hundreds of years. You may also enjoy some of the other benefits of drinking green tea.
- University of Maryland Medical Center – Complementary Medicine: Green Tea.
- C Cabrera et al. Beneficial Effects of Green Tea – A Review. J Am Coll Nutr Apr 2006 vol. 25 no. 2 79-99
- TM Rains et al. Anti-obesity effects of green tea catechins: a mechanistic review. J Nutr Biochem. 2011 Jan;22(1):1-7.
- AG Dulloo et al. Efficacy of a green tea extract rich in catechin polyphenols and caffeine in increasing 24-h energy expenditure and fat oxidation in humans. Am J Clin Nutr December 1999 vol. 70 no. 6 1040-1045.