Does Green Tea Increase Metabolism and Promote Weight Loss?

Green tea is known for its disease fighting health benefits around the world. There has been talk that it can do more than provide powerful antioxidants because it can also boost your metabolism. The question I am pondering is if this popular beverage can rev up metabolism and if it is enough to create a significant amount of weight loss.

The first article I found was on webMD.com on a small study done by Abdul G. Dulloo, a researcher at the University of Geneva, Switzerland, and lead author of the study published in the current issue of the American Journal of Clinical Nutrition. “The study involved 10 healthy young males, none of whom was obese but who ranged from lean to mildly overweight. Each was randomly assigned to each of three meals containing one of three treatments: green tea extract (50 mg of caffeine); 50 mg capsule of caffeine; or a placebo capsule. On three separate occasions, each spent 24 hours in a specially designed respiratory chamber in which researchers could measure energy expenditure and thermogenesis (energy used by digesting and absorbing food), which was increased by 4%, while overall energy expenditure was increased by 4.5%” (“Green Tea Boosts”, 1999). In a 1500 calorie diet, you’d be burning 60 extra calories. The part that contradicts is the small study group of 10 young healthy males, lean to overweight. This doesn’t provide evidence for females or the older population, or people who consume more than 1500 calories a day.  It had a fair conclusion that in this study it sped up fat oxidation and metabolic rates, but it wouldn’t make a big difference for an obese person. I would say this is an evidence based reliable source. There was no author of the news article, but the article included information in it from an individual with noteworthy credentials. This article supported the claim, since metabolism was shown to increase with the consumption of green tea.

My second article was from livestrong.com and gave more of a biochemical approach as to how green tea reacts in your body. The author, Lister, discussed how it boosts metabolism by stimulating the sympathetic nervous system and improves insulin sensitivity by the accompaniment of caffeine and antioxidant compounds called catechins. These inhibit enzymes involved in fat storage and energy regulation. The cellular reactions involved sustain high levels of noradrenalin, which causes your body to oxidize fat at a higher rate. After people took green tea extracts they burned a higher percentage of body fat. Therefore, they also found that catechins also reduce abdominal fat. Also, obese patients benefitted by lowering weight and cholesterol levels from drinking tea or taking supplements. Patience Lister “has been conducting research on natural health products and functional food since 2005. She has been writing since 2009 and has contributed to “Canadian Running Magazine,” “iRun Magazine” and “The Vancouver Sun.” Lister has a Bachelor of Science in biology from the University of Victoria and a diploma in food technology from the British Columbia Institute of Technology” (Lister 2011). Conclusions in this article were based on evidence in several studies found in The American Journal of Clinical Nutrition, The Journal of Nutrition, and The Journal and the AmericanCollege of Nutrition. I would say this is a reliable source that supports the claim.

My third article was found from a website bodybuilding.com. It primarily listed information about what drinking green tea can do, such as drinking 3-5 cups a day can burn an extra 70 kcals/day, which adds up to 7 pounds a year. It discussed how green tea has been shown to inhibit fat absorption, preventing insulin spikes and fat storage and reducing the appetite. The author, Rebekah Baumgardner works as a counselor and life coach specializing in weight management, eating disorders, emotional eating and body image with a Bachelor’s of Science in Psychology. I would say this source is much more commercial than the other ones I found.  No scientific evidence was actually cited, but this article supported the claim.

The fourth article I found was from Google advanced search at about.com. It talks about how green tea may help with weight loss, but drinking it won’t cause you to shed pounds all by itself. The article wrote, “In a 2007 report from the American Journal of Physiology: Regulatory, Integrative and Comparative Physiology, scientists state that green tea may fight the decrease in metabolism that typically accompanies weight loss. According to the report’s authors, green tea may also inhibit the effects of catechol-O-methyltransferase (an enzyme known to trigger the breakdown of brain chemicals involved in regulating appetite)” (Wong 1012).  It also talks about how the antioxidants (catechins) in green tea may increase metabolism. The National Institute of Health cautions the belief of green tea promoting weight loss, due to little scientific evidence. The author, Cathy Wong, is an ND, CNS, a licensed naturaopathic doctor and Certified Nutrition Specialist. Her work supports other references and her conclusions are valid with the information she provides. In order to experience weight loss benefits, green tea should be combined with regular exercise and a healthy diet. This article supports the claim with evidence, but doesn’t prove the claim to be true.

In order to find my scientific research article I went to the OSU library databases and used the Medline PubMed database to search for my topic. I used the terms “green tea” and “metabolism” to search for an article relating to my topic. I found an experimental study on the Metabolic Response to Green Tea Extract During Rest and Moderate- Intensity Exercise. This study was found in the Journal of Nutritional Biochemistry. They conducted the study based on the following information, “green tea catechins have been hypothesized to increase energy expenditure and fat oxidation by inhibiting catechol-O-methyltransferase (COMT) and thus promoting more sustained adrenergic stimulation” (Hodgson et al., 2011). They investigated the effects of green tea ingested for a period of 7 days by 27 healthy, physically active males. The treatment was a placebo-controlled, double-blind study, where 13 males got the green tea extract (GTE) that contained 1200 mg catechins and 240mg caffeine per day and the other group received placebo drinks. After drinking their final drink on day 8, they were asked to rest for 2 hours before performing an hour of moderate intensity cycling. Their blood was drawn before and during exercise. “Plasma was analyzed using untargeted four-phase metabolic profiling and targeted profiling of catecholamines. Results showed that GTE did not enhance adrenaline or noadrenaline during rest or exercise. At rest GTE led changes in metabolite concentrations related to fat metabolism (3-β-hydroxybutyrate), lipolysis (glycerol) and tricarboxylic acid cycle (TCA) cycle intermediates (citrate) when compared to placebo” (Hodgson et al., 2011). The study did not explain if results were statistically significant, nor did it set limitations for age or gender, but it concluded that supplementation resulted in metabolic differences during rest and exercise. I agree with the interpretation, but I believe it could have been clearer and included more numbers so readers would have a better idea of the significance green tea extract has on metabolism.

After examining various articles and searching for evidence that either supports or somewhat supports my claim I have come to the conclusion that green tea does in fact increase metabolism. There isn’t sufficient evidence that it can promote significant weight loss. I couldn’t find any articles refuting the claim. Every article I came upon supported it with some form of evidence or research. I feel they were all conclusive in the fact the green tea increases metabolism, but inconclusive in the idea that it promotes significant weight loss. The component of the idea is factual, but more experiments need to be conducted over varying populations, ages, and genders in order for there to be a conclusive answer. The conclusion so far…drinking green tea or taking supplements increases metabolism, but doesn’t have enough evidence of promoting significant weight loss in varying individuals due to insufficient scientific studies.

References

Baumgardner, R. (2010, August 27). Metabolism: popular myths and 9 easy ways to rev

it up!. Retrieved from http://www.bodybuilding.com/fun/9-tips-to-increase-metabolism.htm

Hodgson, A. B., Randell, R. K., Boon, N., Garczarek, U., Mela, D. J., Jeukendrup, A. E.,

& Jacobs, D. M. (2011). Metabolic response to green tea extract during rest and moderate-intensity exercise. The journal of nutritional biochemistry, doi: 10.1016/j.jnutbio.2012.06.017

Lister, P. (2011, May 24). Does green tea speed up your metabolism?. Retrieved from

http://www.livestrong.com/article/450271-does-green-tea-speed-up-your-metabolism/

Wong, C. (2012, September 19). Green tea for weight loss. Retrieved from

http://altmedicine.about.com/od/greentea/a/green_tea_weight_loss.htm

Green tea boosts metabolism, protects against disease. (1999). Retrieved from

http://www.webmd.com/diet/news/19991128/green-tea-boosts-metabolism-protects-against-diseases

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