Updated: Jan 19
Our weight basically depends on many factors - the number of calories we consume, how many of those we burn up, and how many we store as body fat for later use. Of course, there are other factors that affect body weight which include our genes, our environment, our lifestyle, how efficient our body works, and our relationship with food.
When we burn all the calories that we consume, we maintain our weight. However, if we consume more and burn up less, then we pack on more pounds.
Tea has been the subject of many research studies focused on investigating its effects on weight loss. Specifically, the studies are centered on the group of chemical substances in tea called polyphenols. With high antioxidant properties, the many claims of health benefits from drinking tea, including its weight-loss activity, are due to these polyphenols.
But does drinking tea really help in stripping off unwanted pounds? Can we really just add tea to our diet without changing anything else to keep fit? What does science tell us about this?
1 Tea consumption has the potential to increase energy expenditure and fat oxidation.
Energy expenditure is the total number of calories we burn everyday. Fat oxidation is simply fat burning. After fats are broken down into fatty acids, these are released into the bloodstream and will be captured by hungry cells and used for energy. Energy expenditure and fat oxidation both impact body weight.
Findings from several studies suggest that tea polyphenols exhibit measurable weight loss properties by increasing energy expenditure and fat oxidation. In one study where healthy men were supplemented with green tea extract containing epigallocatechin gallate (EGCG), most abundant in green tea, and caffeine over a 24-hour period, energy expenditure increased significantly and was higher compared with caffeine alone; and fat oxidation was higher with green tea extract compared with caffeine alone.
Results from another study focused on the effects of green tea consumption and resistance training on the body composition and metabolic rate of overweight women show that green tea promoted changes in body composition, weight loss, maintenance of lean body mass, loss of body fat, decreased waist circumference and lowered body fat percentage. Moreover, green tea consumption with resistance training produced the largest gains in lean body mass and strength, as compared with exercise alone.
Though most studies, even using other types of tea, show beneficial effects, there are human trials that did not yield similar results. This points to the fact that the science behind body weight management is complex, and many other factors that affect body weight must be taken into account.
2 Tea polyphenols may help prevent obesity by reducing the absorption of dietary fat and starch resulting to lower calorie intake.
Our body is good at storing fat especially since our fat cells, where fatty acids are packaged and stored, have unlimited capacity. Reducing how much fat we absorb then can help in decreasing calorie intake.
Studies on tea suggest that its polyphenols have the ability to reduce fat absorption by suppressing the activity of a digestive enzyme called pancreatic lipase. Lipase is the major enzyme responsible for breaking down dietary fat in the intestine. When fat is not digested, it is excreted in the feces.
Similarly, tea polyphenols from green and black tea inhibit carbohydrate-digesting enzymes, such as glucosidases, that are involved in breaking down complex carbohydrates such as starch and glycogen. This inhibition limits the digestion and absorption of dietary starch.
It is important to note that our body needs carbohydrates, proteins and fats to build substances necessary for growth, maintenance and activity. The weight control aspect of studies conducted on tea is centered on determining the anti-obesity action of tea polyphenols.
3 There are multiple compounds present in tea that have strong ability to modulate gut microbiota and induce a microbial environment beneficial to obesity prevention.
The gut microbiota is comprised of colonies of bacteria residing in the gastrointestinal tract. It is a community of different types of health-promoting bacteria that plays a variety of functions in metabolism, hunger and digestion. The diversity and balance are important to keep us healthy.
The findings on many studies conducted on tea’s association with weight management are encouraging, and researchers think that these results may be due in part to change at the gut microbiome level. Results from studies suggest that tea extracts (a) can increase the growth of beneficial bacteria in the human intestine implying prebiotic effects, and (b) can ameliorate some of the unfavorable changes in the microbial diversity brought about by high-fat diets and/ or obesity.
Though there are studies that demonstrated significant reduction in body weight from consumption of prebiotics and probiotics, more information is needed to investigate how changes in the gut microbiome level impact body weight.
The Bottom Line
Tea is an important source of antioxidants. Its consumption has been widely studied for its anti-obesity, anti-viral, antibacterial, anti-inflammatory, immune-boosting, and anti-cancer effects.
It may not be the magic bullet though that, when consumed, will immediately strip off all the unwanted pounds. However, sipping a cup or two a day is definitely a step towards a healthier lifestyle. Lifestyle, after all, has a great impact on one’s health, including susceptibility to weight gain.
(1) Abdul G Dulloo, Claudette Duret, Dorothée Rohrer, Lucien Girardier, Nouri Mensi, Marc Fathi, Philippe Chantre, Jacques Vandermander "Efficacy of a green tea extract rich in catechin polyphenols and caffeine in increasing 24-h energy expenditure and fat oxidation in humans,"The American Journal of Clinical Nutrition, Volume 70, Issue 6, December 1999, Pages 1040–1045, https://doi.org/10.1093/ajcn/
(2) P Kapoor, Masaaki Sugita, Yoshitaka Fukuzawa, Tsutomu Okubo “Physiological effects of epigallocatechin-3-gallate (EGCG) on energy expenditure for prospective fat oxidation in humans: A systematic review and meta-analysis,” 2017 May; 43:1-10. DOI: 10.1016/j.jnutbio.2016.10.013
(3) Dylan O’Neill Rothenberg, Caibi Zhou, and Lingyun Zhang “A Review on the Weight-Loss Effects of Oxidized Tea Polyphenols,” Published online 2018 May 14. doi: 10.3390/molecules23051176
(4) R. Hursel W. Viechtbauer A. G. Dulloo A. Tremblay L. Tappy W. Rumpler M. S. Westerterp‐Plantenga “The effects of catechin rich teas and caffeine on energy expenditure and fat oxidation: a meta‐analysis,” First published: 02 March 2011
(5) William Rumpler, James Seale, Beverly Clevidence, Joseph Judd, Eugene Wiley, Shigeru Yamamoto, Shigeru Yamamoto “Oolong Tea Increases Metabolic Rate and Fat Oxidation in Men,” The Journal of Nutrition, Volume 131, Issue 11, November 2001, Pages 2848–2852, https://doi.org/10.1093/jn/131.11.2848
(6) Gabrielle Aparecida Cardoso, Jocelem Mastrodi Salgado, Marcelo de Castro Cesar, and Carlos Mario Donado-Pestana “The Effects of Green Tea Consumption and Resistance Training on Body Composition and Resting Metabolic Rate in Overweight or Obese Women,” Article in Journal of medicinal food, November 2012 DOI: 10.1089/jmf.2012.0062 [Source: PubMed]
(7) Sung I. Koo and Sang K. Noh “Green Tea as Inhibitor of the Intestinal Absorption of Lipids: Potential Mechanism for its Lipid-Lowering Effect,” Published in final edited form as: J Nutr Biochem. 2007 Mar; 18(3): 179–183. doi: 10.1016/j.jnutbio.2006.12.005
(8) Lochocka, K. et al. “Green tea extract decreases starch digestion and absorption from a test meal in humans: a randomized, placebo-controlled crossover study,” Sci. Rep. 5, 12015; doi: 10.1038/srep12015 (2015)
(9) Timothy Bond and Emma Derbyshire “Tea Compounds and the Gut Microbiome: Findings from Trials and Mechanistic Studies,” Published online 2019 Oct 3. doi: 10.3390/nu11102364