For centuries, the intake of green tea in various countries had long been associated with good health and long life. But up to this date, scientific evidences of green tea intake with its weight loss and fat burning properties are still being subjected to debate but recent studies showed promising results. These promising results had also paved the way for the extensive, promotional use of green tea with varying components as fat-burning herbal supplements worldwide.1
Most studies of green tea and weight loss had already been done in rats. In one study, the extract from the green tea plant, Camellia sinensis, had been found to be both anti-hyperglycemic and hypocholesterolmic in diabetic rats.2 Furthermore, aside from showing improved cardiovascular risk indicators and significant protein digestion inhibition, its aqueous extract had also shown preventive effects on the buildup of internal organ fats in rats but only in higher dosages.3
The mechanisms of green tea on its action for weight loss are now being proposed and studied. One proposal says that green tea catechins (GTC) can influence sympathetic nervous system (SNS) activity and therefore promoting energy expenditure and then consequently triggering the oxidation of body fat. Other mechanisms of action include alterations in satiety, decreased nutrient absorption in the gut, and also activation of enzymes involved in hepatic fat oxidation.4 Some enzymes that were found to be linked on its fat burning properties are catechol-O-methyltransferase, acetyl-CoA carboxylase, and fatty acid synthase.5 Moreover, the SNS participates in the regulation of lipolysis, and the sympathetic innervation of white adipose tissue may take part in an crucial role in the regulation of total body fat, in general.6 To date, this multimodal approach had been a more credible explanation to the fat burning process.5
Aside from these mechanisms, it was also found out that caffeine, a natural component from green tea leaves aside from GTC’s, had also been found to assist in the weight loss process.4 Although effective as a weight loss product in green tea leaves with reduction in body mass index (BMI), body weight, waist circumference (WC)7, caffeine had also been well known to have deleterious effects in the human body and thus, decaffeinated green tea products have also been prepared and studied. In these studies, decaffeinated green tea still had its anti-obesogenic effect but at a decreased rate and thus, caffeinated green tea is still advised to be taken for its more significant weight loss effect but it can only in lesser, controlled amount.8
In 2010, a clinical trial had been done among overweight breast cancer survivors and the results showed that decaffeinated green tea intake for 6 months was associated with a slight reduction in body weight and improved high-density lipoproteins (HDL) and glucose homeostasis.9 Other studies had also shown that green tea intake may also play a therapeutic role in nonalcoholic fatty liver disease, a syndrome of progressive liver dysfunction that is closely related to diabetes, obesity and insulin resistance. This hepatoprotective property of green tea, especially its polyphenolic catechins (GTC), may also be a contributing factor for subsequent weight loss.10
REFERENCES
1 Jeukendrup AE, Randell R. Fat burners: nutrition supplements that increase fat metabolism. Obes Rev. 2011 Oct;12(10):841-51.
2 Haidari F, Shahi MM, Zarei M, Rafiei H, Omidian K. Effect of green tea extract on body weight, serum glucose and lipid profile in streptozotocin-induced diabetic rats. A dose response study. Saudi Med J. 2012 Feb;33(2):128-33.
3 Bajerska J, Wozniewicz M, Jeszka J, Drzymala-Czyz S, Walkowiak J. Green tea aqueous extract reduces visceral fat and decreases protein availability in rats fed with a high-fat diet. Nutr Res. 2011 Feb;31(2):157-64.
4 Rains TM, Agarwal S, Maki KC. Antiobesity effects of green tea catechins: a mechanistic review. J Nutr Biochem. 2011 Jan;22(1):1-7. Epub 2010 Nov 5.
5 Thavanesan N. The putative effects of green tea on body fat: an evaluation of the evidence and a review of the potential mechanisms. Br J Nutr. 2011 Nov;106(9):1297-309. Epub 2011 Aug 3.
6 Westerterp-Plantenga MS. Green tea catechins, caffeine and body-weight regulation. Physiol Behav. 2010 Apr 26;100(1):42-6. Epub 2010 Feb 13.
7 Phung OJ, Baker WL, Matthews LJ, Lanosa M, Thorne A, Coleman CI. Effect of green tea catechins with or without caffeine on anthropometric measures: a systematic review and meta-analysis. Am J Clin Nutr. 2010 Jan;91(1):73-81. Epub 2009 Nov 11.
8 Hursel R, Viechtbauer W, Westerterp-Plantenga MS. The effects of green tea on weight loss and weight maintenance: a meta-analysis. Int J Obes (Lond). 2009 Sep;33(9):956-61. Epub 2009 Jul 14.
9 Stendell-Hollis NR, Thomson CA, Thompson PA, Bea JW, Cussler EC, Hakim IA. Green tea improves metabolic biomarkers, not weight or body composition: a pilot study in overweight breast cancer survivors. J Hum Nutr Diet. 2010 Dec;23(6):590-600. doi: 10.1111/j.1365-277X.2010.01078.x. Epub 2010 Aug 27.
10 Masterjohn C, Bruno RS. Therapeutic potential of green tea in nonalcoholic fatty liver disease. Nutr Rev. 2012 Jan;70(1):41-56. doi: 10.1111/j.1753-4887.2011.00440.x.
