I’m sure you’ve heard of the health benefits of green tea before.
It’s natural, it’s green, it has antioxidants, and some people believe it can help prevent cancer and delay ageing.
Now I don’t know about such strong claims, but tea does actually provide a range of health benefits.
But I’m really not going to get into that here.
I’m going to explore how green tea affects your metabolism, and why it has started popping up in the majority of fat loss supplements on the market.
If you look at the ingredients list for a popular fat loss supplement then chances are you will see green tea extract on there.
Compounds in Green Tea
Green tea contains certain active compounds, notably Caffeine and its relatives Theophylline and Theobromine (in small amounts). Caffeine is a well known stimulant, but Theophylline and Theobromine also provide a small effect.
Additionally, Green Tea contains an amino acid known as L-Theanine, which does have a sedative effect that is believed to oppose some of the stimulant effects of Caffeine.
Catechins are another class of compounds that Green Tea contains in abundance, and these are believed to be part of the reason for its health benefits.
The biggest source of these is EGCG (Epigallocatechin Gallate), one of the active compounds in green tea, and likely one of those that can raise metabolism.
Does Green Tea Increase Your Metabolism?
Two placebo-controlled cross-over studies were performed, one with 12 healthy men and the other with 11. They exercised at a moderate intensity, while taking either green tea extract or placebo, and several markers were measured.
The results were that their levels of fat oxidation were 17% higher, and the contribution of carbohydrate to energy expenditure was correspondingly reduced. Their insulin levels were also reduced. This study suggests that green tea extract increases fat oxidation during exercise (1).
A study with 10 healthy men found that green tea extract increased 24 hour energy expenditure by 4%, with the same amount of isolated caffeine showing no effect. This suggests that green tea may increase the metabolic rate, more than can be explained simply by the caffeine content (2).
In one study, 60 obese individuals from Thailand were randomized to either a green tea extract group or a placebo group during a 12 week calorie controlled weight loss period. The group taking green tea extract lost significantly more weight (3).
A trial with 132 obese individuals found that green tea extract didn’t change total fat mass compared to caffeine, but found that green tea caused a significantly greater fat loss in the abdominal area (4).
However, there have also been some studies where green tea doesn’t raise the metabolic rate, and doesn’t lead to improved weight loss results compared to placebo (5, 6).
Conclusion
My take on these studies is that green tea may cause a modest, temporary increase in the metabolic rate and may slightly increase fat oxidation.
The mechanism suggested is that the catechins in green tea partially inhibit an enzyme that breaks down the neurotransmitter Noradrenaline (usually stimulating), effectively increasing its effects and contributing to increased fat burning.
Personally, I think that green tea may provide a modest weight loss benefit, but its effects are so minor that they are dwarfed by any possible effect caused by a healthy diet and exercise program.
But for those who are already doing all the right things and need a small push, green tea may give a tiny boost in the right direction.
Cool article Kris! I do drink green tea quite often but not necessarily for the weight loss or metabolism increase. I just like it and it’s nice that you’ve gathered these studies together.
btw … your site is FAST :D
What’s the main culprit, or is there one?
Hey Kevin, thanks. I did a bunch of things, the main thing is removing most of the social widgets and clutter. Then I upgraded to a dedicated server and optimized the custom css/php code as much as I could.
n=1, green tea may also reduce hunger a bit in some people. It is a good alternative to coffee, with 1/3 the caffeine, and a lesser diuretic effect. Not as good as water, but better than coffee. Less bad.
Keep up the fine work.
Good to see some controlled studies of this – and even better to hear that there is a positive, if minor, benefit. Every little bit helps, right? Thanks for continuing to keep us informed it is SO helpful!!
I have always wondered how big of an impact green tea made on losing weight/burning calories/etc. From my experience, I really haven’t noticed a difference from drinking green tea in terms of losing weight.
Since green tea contains caffeine, I wonder how big of an impact it has on your adrenal glands. If someone were to drink gallons and gallons of green tea each day in order to “boost their fat burning,” would this eventually cause adrenal fatigue?
Hi Robert,
I would caution excessive use of green tea for just this reason, especially given the adrenally stressful life that many people now live.
Many of my clients find that cycling of such products negates the potential stress of such an approach.
Hope this helps,
george
Nice post. Please don’t eat your cat.
Hi Kris,
Indeed your site does load very fast, good job, the cat can consider itself safe, for the moment….
One thing your review got me wondering is how to explain the differences between the studies that showed a response, and those that didn’t?
Sadly I don’t have a uni subscription that would allow me to look more deeply into this question, but I suspect you do. What do you think?
Cheers and Keep Up The Good Work,
George Super Boot Camps
Hello George, I suppose it may have something to do with the small sample sizes.
Hi Kris. Thanks for this site, finally someone is telling us the truth with the reasons and references. However, my conclusion and answer to the question, after reading this about Green Tea would simply be: It’s hard to say :)
I only know that Green Tea makes me feel hungry and nauseous at the same time.
Hi Maria,
I’d say your personal response is one that many others have also experienced. What I find in my client work is that everyone responds differently, and that’s totally ok.
The whole point of my work with clients is to help them through the maze of discovery that diet and nutrition is. That’s also no different for me, an I do genuinely enjoy the journey. It’s funny that in all my studies the information is delivered about generalisations, but then is ALWAYS qualified by the lecturer/teacher informing that these instructions are a starting point and need to be refined and adapted to suit the reactions and needs seen whilst working with individuals. That’s why we need to have a protocol to assess and evaluate our dietary and physical progress. Unfortunately, it seems to me that this protocol or advice is generally lacking in most public nutrition documentation.
(apologies to Kris for a comment hijack:)
Hope this helps,
George SuperBootCamps.
I drink green tea as a refreshing drink, and for the health benefits. I had heard of its uses in speeding up the metabolism as an aid to weight loss, but always felt the effect would be minimal. Seems your conclusions support that.
Hey Kris,
Great post. I’m personally a fan of green tea and rotate between a wide range of hot beverages throughout the day. I think when it comes to metabolism it’s a collective effort. No one thing can have a massive impact in isolation but if you eat, drink and do all the things you should be doing to keep your metabolism healthy and revved up, it will improve quite significantly.
Tom
I don’t think I’ve lost any weight because of it, but I usually start my day off with a cup of green tea. Coffee has always caused me to “crash” at about 1 pm, so tea has been a great alternative.
- Austin
Heya Kris,
yeah Green Tea is awesome, but really much more for the numerous health benefits, and the appetite suppressing effect it has than for weight loss, like you said.
I drink Green Tea regular and the most noticeable improvement was in my immune system: Since starting out I didn’t get a flu for some 7 years! :-)
Mark