Green Tea has long been associated with health benefits. Recent research indicates that it may hold promise as a treatment for obesity and other weight problems. It is believed that more than half of Americans are either overweight or obese. These conditions are strongly associated with complications like type 2 diabetes mellitus, hypertension, heart disease, gall bladder disease, and sleep apnea. Losing weight can help alleviate some of these symptoms. Researchers have found that Green Tea increases the amount of energy spent by the body, and thus possibly contributes to a weight loss benefit. [3] Other research seems to confirm green tea's potential as a weight loss aid. A team of doctors working at the University of Geneva concluded that "Green Tea has thermogenic properties and promotes fat oxidation beyond that explained by its caffeine content per se." [4] Similar research conducted by doctors in Switzerland also confirms the thermogenic properties of green tea. [5]

Abstracts of Clinical Studies of
Green Tea and Weight Loss

Green tea reduces body fat accretion caused by high-fat diet in rats through beta-adrenoceptor activation of thermogenesis in brown adipose tissue.

J Nutr Biochem. 2003 Nov;14(11):671-6.

Choo JJ.

Department of Foods and Nutrition, Kunsan National University, Kunsan, Cheollabuk-do 573-701, South Korea. jjchoo@kunsan.ac.kr

The aim of the present study was to investigate body fat-suppressive effects of green tea in rats fed on a high-fat diet and to determine whether the effect is associated with beta-adrenoceptor activation of thermogenesis in brown adipose tissue. Feeding a high-fat diet containing water extract of green tea at the concentration of 20g/kg diet prevented the increase in body fat gain caused by high-fat diet without affecting energy intake. Energy expenditure was increased by green tea extract which was associated with an increase in protein content of interscapular brown adipose tissue. The simultaneous administration of the beta-adrenoceptor antagonist propranolol(500 mg/kg diet) inhibited the body fat-suppressive effect of green tea extract. Propranolol also prevented the increase in protein content of interscapular brown adipose tissue caused by green tea extract. Digestibility was slightly reduced by green tea extract and this effect was not affected by propranolol. Therefore it appeared that green tea exerts potent body fat-suppressive effects in rats fed on a high-fat diet and the effect was resulted in part from reduction in digestibility and to much greater extent from increase in brown adipose tissue thermogenesis through beta-adrenoceptor activation.

PMID: 14629899 [PubMed - in process]

Iron bioavailability and weight gains to iron-deficient rats fed a commonly consumed Tunisian meal 'bean seeds ragout' with or without beef and with green or black tea decoction.

J Trace Elem Med Biol. 2003;17(3):159-64.

Hamdaoui MH, Chabchoub S, Hedhili A.

Unite de Recherche sur L'Anemie Nutritionnelle et la Biodisponibilite des Oligo-elements, Ecole Superieure des Sciences et Techniques de la Sante de Tunis, Tunis, Tunisia. hamadaoui.medhedi@gnet.tn

The Fe bioavailability and the weight gains were evaluated in rats fed a commonly consumed Tunisian meal 'bean seeds ragout' (BSR), with or without beef and with black or green tea decoction. The Fe bioavailability was evaluated in Fe-deficient rats by the hemoglobin repletion method and the Fe stored in the liver. The addition of beef to the BSR significantly increased the Fe bioavailability from this meal by 147% and the reserve of Fe stored in the liver by 77% (P < 0.001). In contrast, both black and green tea decoctions caused a significant decrease of the Fe bioavailability from BSR meal (-19.6 +/- 4.9% and -14.9 +/- 4.1%, respectively). The reserve of Fe stored in the liver was significantly lower in the BSR, the black and the green tea groups than in the positive control group (FeSO4). The weight gains were significantly lower in the black and the green tea groups (3.9 +/- 5.7 g, 13 +/- 1.9 g, respectively) than in the BSR group (24.9 +/- 6 g). The addition of beef to BSR meal counteracted the inhibitory effect of the kidney bean and considerably improved the Fe bioavailability and the Fe stored in the liver of rats. The green tea decoction, which constitutes an important source of antioxidant factors, had the same inhibitory effect as the black tea decoction on the Fe bioavailability from BSR meal. In addition, both black and green teas significantly reduced the weight gains, where the black tea decoction has the most effect.

PMID: 14968927 [PubMed - in process]

Recent findings of green tea extract AR25 (Exolise) and its activity for the treatment of obesity.

Phytomedicine. 2002 Jan;9(1):3-8.

Chantre P, Lairon D.

Laboratoires Arkopharma, Carros, France. r-d@arkopharma.com

The green tea extract AR25 is an 80% ethanolic dry extract standardized at 25% catechins expressed as epigallocatechin gallate (EGCG). In vitro, green tea extract AR25 exerts a direct inhibition of gastric and pancreatic lipases and a stimulation of thermogenesis. In an open study, the effects of extract AR25 were evaluated in moderately obese patients. After 3 months, body weight was decreased by 4.6% and waist circumference by 4.48%. These results suggest the green tea extract AR25 to be a natural product for the treatment of obesity, which exerts its activity by several ways: inhibition of lipases and stimulation of thermogenesis.

PMID: 11924761 [PubMed - indexed for MEDLINE]

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. 1999 Dec;70(6):1040-5.
Am J Clin Nutr. 2000 Nov;72(5):1232-4.

Dulloo AG, Duret C, Rohrer D, Girardier L, Mensi N, Fathi M, Chantre P, Vandermander J.

Department of Physiology, Faculty of Medicine, University of Geneva. abdul.dulloo@unifr.ch

BACKGROUND: Current interest in the role of functional foods in weight control has focused on plant ingredients capable of interfering with the sympathoadrenal system. OBJECTIVE: We investigated whether a green tea extract, by virtue of its high content of caffeine and catechin polyphenols, could increase 24-h energy expenditure (EE) and fat oxidation in humans. DESIGN: Twenty-four-hour EE, the respiratory quotient (RQ), and the urinary excretion of nitrogen and catecholamines were measured in a respiratory chamber in 10 healthy men. On 3 separate occasions, subjects were randomly assigned among 3 treatments: green tea extract (50 mg caffeine and 90 mg epigallocatechin gallate), caffeine (50 mg), and placebo, which they ingested at breakfast, lunch, and dinner. RESULTS: Relative to placebo, treatment with the green tea extract resulted in a significant increase in 24-h EE (4%; P < 0.01) and a significant decrease in 24-h RQ (from 0.88 to 0.85; P < 0.001) without any change in urinary nitrogen. Twenty-four-hour urinary norepinephrine excretion was higher during treatment with the green tea extract than with the placebo (40%, P < 0.05). Treatment with caffeine in amounts equivalent to those found in the green tea extract had no effect on EE and RQ nor on urinary nitrogen or catecholamines. CONCLUSIONS: Green tea has thermogenic properties and promotes fat oxidation beyond that explained by its caffeine content per se. The green tea extract may play a role in the control of body composition via sympathetic activation of thermogenesis, fat oxidation, or both.

PMID: 10584049 [PubMed - indexed for MEDLINE]

Effects of green tea on growth, food utilization and lipid metabolism in mice.

In Vivo. 2000 Jul-Aug;14(4):481-4.

Sayama K, Lin S, Zheng G, Oguni I.

Department of Animal Science, Faculty of Agriculture, Shizuoka University, Japan.

To find whether green tea has anti-obesity effects in mice, female ICR mice were fed on diets containing 1, 2 and 4% green tea powder for 16 weeks and the body weight and food intake were weighed. After the administration of green tea, the ovaries, kidneys, adrenals, liver, spleen, brain, pituitary and intraperitoneal adipose tissues in the mice were weighed and lipid levels in the serum and in the liver and serum leptin levels were measured. It was found that body weight increase and intraperitoneal adipose tissues were remarkably suppressed by the administration of diets containing 2 and 4% green tea powder. Food intake was suppressed by feeding the 4% green tea diet. Concentrations of total cholesterol in the liver, triglycerides in serum and liver and nonestrified fatty acids in serum from mice which were administered green tea diet were lower than those in the controls. Leptin levels in serum showed a decrease with green tea treatments. These results indicated that lipid metabolism in mice was suppressed by the administration of green tea powder and thereby the fatty accumulation and body weight increase was suppressed.

PMID: 10945161 [PubMed - indexed for MEDLINE]

Green tea and thermogenesis: interactions between catechin-polyphenols, caffeine and sympathetic activity.

Int J Obes Relat Metab Disord. 2000 Feb;24(2):252-8.

Dulloo AG, Seydoux J, Girardier L, Chantre P, Vandermander J.

Institute of Physiology, University of Fribourg, Fribourg, Switzerland. abdul.dulloo@unifr.ch

The thermogenic effect of tea is generally attributed to its caffeine content. We report here that a green tea extract stimulates brown adipose tissue thermogenesis to an extent which is much greater than can be attributed to its caffeine content per se, and that its thermogenic properties could reside primarily in an interaction between its high content in catechin-polyphenols and caffeine with sympathetically released noradrenaline (NA). Since catechin-polyphenols are known to be capable of inhibiting catechol-O-methyl-transferase (the enzyme that degrades NA), and caffeine to inhibit trancellular phosphodiesterases (enzymes that break down NA-induced cAMP), it is proposed that the green tea extract, via its catechin-polyphenols and caffeine, is effective in stimulating thermogenesis by relieving inhibition at different control points along the NA-cAMP axis. Such a synergistic interaction between catechin-polyphenols and caffeine to augment and prolong sympathetic stimulation of thermogenesis could be of value in assisting the management of obesity. International Journal of Obesity (2000) 24, 252-258

PMID: 10702779 [PubMed - indexed for MEDLINE]

Twenty-four-hour energy expenditure and urinary catecholamines of humans consuming low-to-moderate amounts of medium-chain triglycerides: a dose-response study in a human respiratory chamber.

Eur J Clin Nutr. 1996 Mar;50(3):152-8.
Comment in: Eur J Clin Nutr. 1997 Oct;51(10):713-5.

Dulloo AG, Fathi M, Mensi N, Girardier L.

Department of Physiology, Faculty of Medicine, University of Geneva, Switzerland.

OBJECTIVE: To determine whether medium-chain triglycerides, in low-to-moderate amounts consumed with meals (at breakfast, lunch and dinner), can increase daily energy expenditure (EE) and 24-h urinary excretion of catecholamines in humans. DESIGN: Dose-response study conducted under double-blind randomised design. SETTING: Respiratory chamber at the Faculty of Medicine, University of Geneva. SUBJECTS: Eight healthy young men were recruited from the student population by advertisement in our Faculty. METHODS: 24-h EE and urinary catecholamines were measured in each subject during stay in a respiratory chamber on four separate occasions. These were randomised between four different combinations of medium-chain triglycerides (MCT) and long-chain triglycerides (LCT), a total 30g/day, which was consumed with their habitual diet in three equal parts (10g each) at breakfast, lunch, and dinner in the following ratio of MCT: LCT (g/g) 0:30, 5:25, 15:15 and 30:0. RESULTS: 24-h EE increased significantly with increasing MCT:LCT ratio (ANOVA, P < 0.001), with the diet providing a total of 15-30 g MCT per day stimulating 24-h EE by 5%: this corresponds to a mean absolute increase in daily EE of approximately 500kJ, with individual values varying between 268 kJ and 756 kJ. No significant differences were observed in respiratory quotient nor in urinary nitrogen losses across diets, but 24-h urinary noradrenaline was significantly increased (ANOVA, P < 0.025), whereas adrenaline and dopamine were unaltered. CONCLUSIONS: This study suggests that relatively low-to-moderate intake of MCT (15-30 g per day) as part of habitual diet may play a role in the control of human body composition by enhancing daily EE, and that this effect is mediated at least in part through activation of the sympathetic nervous system.

PMID: 8654328 [PubMed - indexed for MEDLINE]

http://www.ajcn.org/cgi/content/full/70/6/1040