When discussing whether or not green tea is good for weight loss, the first thing we need to do is clear up exactly what we're talking about. There are a lot of green tea based supplements, using various extracts, L Theanine, Caffiene etc, that have results that will be substantially different to green tea itself as they are in much higher concentration that you'll get from simply drinking green tea.
The studies on whether or not drinking green tea helps weight loss are split pretty much down the middle, with some showing results and others not. The studies that were done on simply drinking green tea, without specific alterations to behaviour were generally less effective with only about 30% showing positive results, and these were not particularly notable.
Although it is likely that participants will have altered the diets slightly as most people will drink less higher calorie alternatives, or eat less from the feeling of fullness that comes as a result of being more hydrated in general. [1] (There are mulitiple studies that show drinking more water helps people lose weight as they eat less and the same could easily apply here).
The studies which green tea was added to other lifestyle changes, exercising more or dieting, the groups that drank green tea were generally more successful at losing weight, but it was not hugely significant. [2]
Green tea based supplements such as L Theanine have shown more substantial results in trials. [3]
Short Answer: Drinking Green Tea can have some minimal effect on weight loss, but there are better options, it will however, be particularly effective if you're replacing a sugary drink with green tea as a result of lowering calorie intake.
Green Tea Weight Loss Studies
Green tea is believed to promote weight loss by boosting the body's metabolism. The metabolism refers to the processes that convert food and drink into energy. Green tea contains caffeine and a type of flavonoid called catechin, both of which have been found to potentially speed up metabolism. Catechin can help break down excess fat, while both catechin and caffeine can increase the body's energy expenditure.
A review published in 2010 found that green tea supplements, containing catechins or caffeine, had a small but positive impact on weight loss and weight management. [4]
A more recent review concluded that while drinking green tea did have a positive effect on weight loss, the result was not statistically significant and unlikely to be of clinical importance. [5]
It is important to note that the doses of catechin and caffeine used in research studies are often higher than what would be found in a typical cup of green tea. Therefore, any potential benefits of green tea for weight loss are likely to be minimal compared to other proven weight loss strategies such as regular exercise and a healthy diet.
A Cultural Seperation of Green Tea Weight Loss Evidence
Generally speaking a lot of trials on green tea and weight loss are conducted in japan and whilst these are high quality trials, green tea is generally more commonly used by the general population. And because it is likely that it was already a common drink for the participants results of drinking green tea for weight loss seem to vary significantly from the west where green tea isn't as common a part of the diet. The trials themselves discussed additional green tea, rather than total green tea in several cases.
To put it simply, it's quite likely that a reasonable portion of the japanese trial participants were simply adding 1 or 2 cups of green tea in, to an existing intake of 1-3 cups, whereas in the west it seems that the participants were not drinking it before hand.
The other mechanism for weight loss as a result of green tea could of course be the phytogenes (the active ingredients) in green tea, but of course once again, the trial participants in japan were likely to already be consuming a lot of these through green tea, or other products containing green tea extracts meaning they were getting much more of the compounds.
This also explains why we generally see more positive results from green tea extracts that are far more concentrated than what you would get from a single cup of green tea.
Both still show some positive results, meaning that the tea itself does likely have some benefit to weight loss, but you may well need more of it than you'd get by simply adding a singular cup to your diet.
Trials Conducted Outside Japan
Six randomly controlled trials conducted outside Japan, involving a total of 532 participants, were similar enough to allow for a meta-analysis. The results showed a very small, statistically nonsignificant mean difference in weight loss favoring green tea preparations over the control group. While the difference was not significant, it suggests a potential benefit of green tea in weight loss.
Trials Conducted in Japan
Eight RCTs conducted in Japan, with a total of 1030 participants, were not similar enough to be pooled together for analysis. However, individually, these trials indicated that participants in the green tea group lost on average 1.2 to 3.5 kg more than those in the control group. Although the results were more promising than the trials conducted outside Japan, further research is needed to draw definitive conclusions. [6]
Green Tea Side Effects
While green tea has been generally considered safe, it's important to note that some adverse effects were reported in the studies. The most commonly reported adverse effects were mild to moderate and included hypertension and constipation.
How Does Green Tea Effect Weight Loss
To understand how green tea might aid in weight loss, it's essential to explore its mechanisms of action. Green tea contains catechins, a type of antioxidant that has been shown to have thermogenic properties. Thermogenesis is the process by which the body produces heat, resulting in increased calorie expenditure. By promoting thermogenesis, green tea may help the body burn more calories, potentially leading to weight loss. [7]
Furthermore, green tea has been found to increase fat oxidation, the process of breaking down stored fat for energy. This effect may contribute to weight loss by reducing fat storage and promoting the use of existing fat stores.
Other Potential Health Benefits of Green Tea
Beyond weight loss, green tea has been associated with several other health benefits. These include:
- Reducing cholesterol levels
- Improving heart functioning
- Lowering the risk of Alzheimer's disease
- Managing type 2 diabetes
- Possessing anti-cancer properties
It is important to note that the evidence for many of these claims remains inconclusive, and further high-quality, long-term studies are needed to confirm the extent of green tea's benefits for various medical conditions.
Is Green Tea Good For Weight Loss Conclusion
In summary, while green tea may have some potential benefits for weight loss, the evidence supporting its efficacy is limited. Any effects on weight loss are likely to be minimal, and the impact of green tea is not as significant as other proven weight loss methods such as exercise and a healthy diet. Green tea can be a valuable addition to a balanced lifestyle, but it should not be relied upon as a sole solution for weight management.
References
1 - https://pubmed.ncbi.nlm.nih.gov/18787524/
2 - https://pubmed.ncbi.nlm.nih.gov/32372444/
3 - https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9014247/
4 - https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2855614/
5 - https://pubmed.ncbi.nlm.nih.gov/23235664/
6 - https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4025876/
7 - https://pubmed.ncbi.nlm.nih.gov/17201629/
