Green tea for weight loss, fact or fiction?
Supporting evidence on the claims about weight-loss effects of green tea
Obesity is, together with cancer, one of the 21st century problems in developed countries, contributing to increased mortality. According to data from the National Health and Nutrition Examination Survey (NHANES) 2003–2006 and 2007–2008, over two-thirds of adults in the United States are overweight or obese, and over one-third are obese [1,2].
Fortunately some scientists and researchers keep on investigating some foods or supplements such as green tea, fiber, and calcium supplements or dairy products that may complement a healthy lifestyle to produce small weight losses or prevent weight gain over time . Image left: China green tea by Marius B under Creative Commons License (CC BY 2.0).
Some of the properties and health benefits of green tea, rich in Polyphenols, and some of the active constituents that may be linked to this weight-loss properties are discussed in this article.
Common name: Green tea
Green tea extract high in catechins reduces body fat 
More a more our society is bombarded with adverts on how to loose weight fast and easy making use of weight-loss supplements, however while some weight-loss supplements produce modest effects (<2 kg weight loss), many have either no or few randomized clinical trials examining their effectiveness, having no strong research evidence indicating that a specific supplement will produce significant weight loss (>2 kg), especially in the long term . Image left: Tea leaf 八十八夜 by 4510waza under Creative Commons License (CC BY-SA 2.0).
Natural and healthy products, such as green tea and proteins, canprevent weight gain or even induce weight loss when consumed in adequate amounts. Green tea has been shown to increase 24 hours and long-term energy expenditure and fat oxidation and also has a positive effect on body-weight regulation [2,3,4,5].
GREEN TEA AND INULIN ANTI-OBESITY EFFECT
Inulin, a naturally occurring polysaccharides produced by many types of plants as garlic and onions among many others that belongs to a class of dietary fibers known as fructans , has been discovered to exert an anti-obesity effect when combined with catechin-rich green tea .
The study, involving a total of thirty subjects divided into a control group and an experimental group who received 650 ml tea or catechin-rich green tea plus inulin, showed how the experimental group receiving the combination of catechin-rich green tea and inulin, experienced a reduction of body weight ( - 1·29 (sem 0·35) kg) and fat mass (0·82 (sem 0·27) kg) with no adverse effects observed.
Additionally after consumption was interrupted for a period of 2 weeks, sustained effects on body weight and fat mass were observed, with which it could be concluded that continuous intake of catechin-rich green tea in combination with inulin for at least 3 weeks may be beneficial for weight management.
GREEN TEA POLYPHENOLS AND BODY WEIGHT
In a study done in high-fat induced rats, green tea Polyphenols exerted beneficial effects on body weight , regulating obesity-related genes, anti-inflammation, anti-oxidant capacity, and estrogen-related actions .
GREEN TEA AND MILK DIET
It seems that this effect is achieved by the diet-induced thermogenesis that the combination of both, green tea and milk protein, exerts on humans, showing how green tea and proteins can induce weight loss when consumed in adequate amounts. These effects are possibly due to the complexes formed between proteins and teapolyphenols . Image left: Homemade pearl milk tea by E.t under Creative Commons License (CC BY-SA 2.0).
Green tea is even more effective on weight reduction when combined with milk protein
SIDE EFFECTS AND WARNINGS
Weight-loss supplements containing metabolic stimulants (e.g., caffeine, ephedra, synephrine) are most likely to produce adverse side effects and should be avoided .
 Green tea polyphenols reduce body weight in rats by modulating obesity-related genes.
Lu C, Zhu W, Shen CL, Gao W.
Department of Environmental Toxicology, The Institute of Environmental and Human Health, Texas Tech University, Texas Tech University Health Sciences Center, Lubbock, Texas, United States of America.
 Weight-control Information Network website. Available: http://win.niddk.nih.gov/statistics/#overweight. Accessed: 2012 May 10.
 Dietary supplements for improving body composition and reducing body weight: where is the evidence?
Dept. of Nutrition and Exercise Sciences, Oregon State University, Corvallis, OR, USA.
 Green Tea Prevents Obesity by Increasing Expression of Insulin-like Growth Factor Binding Protein-1 in Adipose Tissue of High-Fat Diet-Fed Mice.
Ueda M, Ashida H.
Department of Agrobioscience, Graduate School of Agricultural Science, Kobe University , 1-1 Rokkodai-cho, Nada-ku, Kobe, Hyogo 657-8501, Japan.
 Effect of green tea extract on body weight, serum glucose and lipid profile in streptozotocin-induced diabetic rats. A dose response study.
Haidari F, Shahi MM, Zarei M, Rafiei H, Omidian K.
Nutrition Research Center, Ahvaz Jundishapur University of Medical Sciences, Ahvaz, Iran.
 Dulloo A.G., Duret C., Rohrer D., Girardier L., Mensi N., Fathi M., Chantre P., Vandermander J. 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;70:1040–1045.
 Berube-Parent S., Pelletier C., Dore J., Tremblay A. Effects of encapsulated green tea and Guarana extracts containing a mixture of epigallocatechin-3-gallate and caffeine on 24 h energy expenditure and fat oxidation in men. Br. J. Nutr. 2005;94:432–436.
 Westerterp-Plantenga M.S., Lejeune M.P., Kovacs E.M. Body weight loss and weight maintenance in relation to habitual caffeine intake and green tea supplementation. Obes. Res. 2005;13:1195–1204.
 Auvichayapat P., Prapochanung M., Tunkamnerdthai O., Sripanidkulchai B.O., Auvichayapat N., Thinkhamrop B., Kunhasura S., Wongpratoom S., Sinawat S., Hongprapas P. Effectiveness of green tea on weight reduction in obese Thais: A randomized, controlled trial. Physiol. Behav. 2008;93:486–491.
 Wikipedia article on inulin.
 Beneficial effects of catechin-rich green tea and inulin on the body composition of overweight adults.
Yang HY, Yang SC, Chao JC, Chen JR.
Department of Nutrition, I-Shou University, Yanchao District, Kaohsiung City, Taiwan, ROC.
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