Health or Hoax? Green Tea Extract

By Ari Snaevarsson, Features Editor


In this article, we will be examining the health benefits of yet another supplement, but, this time, I will learn from my mistakes and limit my examination to its implications for fat loss. Because it helps neither me nor my readers to chaotically jump from one effect to another fundamentally different one and risk being careless in my review.

Most of green tea extract (GTE)’s health benefits, especially its fat loss effects, are the product of a type of flavanol (natural antioxidants) called catechins. The primary catechin concerned with this discussion is called epigallocatechin-3-gallate (EGCG). Just understand that this is the source of most of the effects found below.


The first study I looked at found GTE supplementation in between moderate-intensity exercise bouts increased fat oxidation versus the placebo by 17% and contribution of fat oxidation to total energy expenditure by a similar percentage (meaning more fat was being recruited as a fuel source for the exercise)1. Let us note here the dosage of GTE catechins was 890mg.

Another study with a little over 100 people per group found continuous ingestion of GTE led to significant reductions in body fat, along with systolic blood pressure and LDL count2. The dosage here was around 583mg.

Here is where things get interesting. A cross-over study looked at energy expenditure (EE) in 12 men consuming either water, full-strength catechin-rich Oolong tea, half-strength Oolong tea, or water with caffeine3. The catechin-rich tea (which ended up equating to a 662mg dosage) caused a 12% increase in fat oxidation rates compared to the water. The half-strength tea (around 331mg) showed no difference.

An intriguing meta-analysis that looked at a myriad of studies concluded GTE intake exerts no statistically significant difference on weight loss for overweight or obese individuals, yet no dosage was specified4. They did find a small decrease on percentage of fat mass, but it was deemed not clinically relevant.

Yet another major literature review on GTE concluded they “could be beneficial against high-fat diet-induced obesity and Type II diabetes.”5 So what is the verdict then, with the two conflicting takeaways of these reviews?

What seems to be the case is the existence of a dose-dependent relationship between catechin intake and fat loss; in other words, its fat loss effects only appear to show themselves at higher dosages, probably north of the 400mg mark.

Something else must be noted when considering appropriate dosing strategies. Kurtis Frank, author at, notes that while GTE’s fat loss effects are astounding in vitro, the ability of catechins to enter the cell varies greatly from one person to the next. For this reason, supplementing high omega-3 fish oil or the flavanol quercetin may improve bioavailability of GTE.


My final words on the matter would be that I was pleasantly surprised at the findings I came across in researching for this article. It is no secret that I prioritize heavily what works in practice over what works in vitro, or even in some controlled studies. A 17% increase in fat oxidation for 12 guys in a lab sounds great, but the general population should be asking themselves what an increase in fat oxidation alone means for actual fat loss, how repeatable such trials are, whether any significance exists in the fact that GTE ingestion occurred between exercise bouts, and what a 17% increase in rates of fat loss even translates into (make a major note of the fact that this is not at all saying they lost 17% more fat, as most would read into this).

My theme of nitpicking for the conclusion of each supplement review I do is not merely a talking point, but just another effort of mine to ensure these findings are not read incorrectly by those not accustomed to reading scientific studies.

Could GTE supplementation in combination with a low-calorie diet and exercise routine prove to exert some fat loss effects? Absolutely. The major takeaway should be that this is a supplement that deserves profoundly more research, as it offers some potentially interesting effects.


  1. Venables, Michelle C., Carl J. Hulston, Hannah R. Cox, and Asker E. Jeukendrup. “Green Tea Extract Ingestion, Fat Oxidation, and Glucose Tolerance in Healthy Humans.” The American Journal of Clinical Nutrition 87, no. 3 (March 2008): 778–84.
  2. Nagao, Tomonori, Tadashi Hase, and Ichiro Tokimitsu. “A Green Tea Extract High in Catechins Reduces Body Fat and Cardiovascular Risks in Humans.” Obesity (Silver Spring, Md.) 15, no. 6 (June 2007): 1473–83. doi:10.1038/oby.2007.176.
  3. Rumpler, W., J. Seale, B. Clevidence, J. Judd, E. Wiley, S. Yamamoto, T. Komatsu, T. Sawaki, Y. Ishikura, and K. Hosoda. “Oolong Tea Increases Metabolic Rate and Fat Oxidation in Men.” The Journal of Nutrition 131, no. 11 (November 2001): 2848–52.
  4. Baladia, Eduard, Julio Basulto, María Manera, Rodrigo Martínez, and David Calbet. “[Effect of green tea or green tea extract consumption on body weight and body composition; systematic review and meta-analysis].” Nutrición Hospitalaria 29, no. 3 (2014): 479–90. doi:10.3305/nh.2014.29.3.7118.
  5. Chacko, Sabu M, Priya T Thambi, Ramadasan Kuttan, and Ikuo Nishigaki. “Beneficial Effects of Green Tea: A Literature Review.” Chinese Medicine 5 (April 6, 2010): 13. doi:10.1186/1749-8546-5-13.


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