February 27, 2009

Green Tea Weight Loss - Backed By Science?

Green tea weight loss have been both lauded as effective, and criticised as being a child of advertising without evidence that it works in weight loss. So what's the truth?

Studies relating to green tea and weight loss

I went looking for studies that would either support or disprove green tea weight loss. Contrary to some critics, I found both studies in the animal AND human model that are very promising.

Animal studies are currently used by mainstream science for leads as to whether something is worth proceeding to human studies on. There are a lot of drawbacks to animal studies, one of the main ones (aside from the pain caused to the animal) is that for different species of animals, you get different results. And that can lead to false conclusions as to whether what is being studied, like green tea weight loss, is effective.

There were a number of studies done with humans in relation to green tea weight loss, however.

Firstly, the green tea and weight loss studies in animals (mice)

The University of Chicago's Tang Center for Herbal Medical Research on epigallocatechins (EGCG) (which are part of green tea) - shows blood levels of glucose (sugars), lipids (fats), and cholesterol are reduced. And fat deposits under the skin and in the abdomin are also reduced. 
Another green tea weight loss study described in the health section of the msn site also found that green tea extract improved the metabolism of glucose and lipids, which is beneficial for weight loss 
There have been a number of green tea weight loss studies done on the ability of green tea extract to lower blood sugar. This relates to our metabolism, energy levels, insulin production and hence could be useful to the dieter in terms of cravings, and maintaining their energy levels. 
But what about studies that support weight loss with green tea in humans?

In this particular green tea weight loss study, oolong tea or green tea extract (an extract is more concentrated than just drinking it on its own) resulted in an increase in energy used by the body of 3-4% (on average). The Linus Pauling Institute say this effect of green tea weight loss is "apparently due to increased fat oxidation and thermogenesis". Thermogenisis refers to energy used in heat production that is not related to resting metabolism or physical activity. (our bodies use energy even when we're doing nothing. It's less than energy used in other activities, of course).

In another study, different groups of people were given caffeine, to see how that compared to green tea in thermogenesis. And people taking the green tea had higher thermogenesis than those taking the equivalent amount of caffeine without green tea catchetins.

Green tea does contain caffeine, but you can get herbal preparations without the caffeine. The good news for people who don't like caffeine, is that it is the catchetins that produce green tea's thermogenesis effects, not the caffeine.

So green tea weight loss can help dieters (not just mice :-) ).

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