I also should mention quickly that keep in mind no fat loss supplement will be effective without proper diet and exercise. Eating a well-balanced diet, comprised of whole grains, fruits, veggies, lean proteins and healthy fats is the way to go along with a regular dose of exercise. Never think any pill or potion, no matter how appealing it sounds, will give you that six-pack you've long been yearning for.
Also, I apologize in advance-this one gets a bit technical, but it's all very necessary to know the how's and why's of what folks may be putting in their bodies.
Green tea extract has recently seen a surge in popularity; it is hard not to find it on the ingredient list of fat loss supplements. Even green tea as a beverage has surged in popularity as it is the most widely consumed beverage in the world, second only to water.
The particular extract in green that is of importance is epigallocatechin-3-gallate (EGCG), which is one of four catechins found in green tea. Among the four, EGCG has showed promised as an adjunct to an effective diet and exercise regimen. However, it is not only the EGCG that appears to be relevant in green tea, but also the naturally occurring caffeine. There is approximately 10-80 mg of caffeine/cup and EGCG and caffeine are synergistic in the process of increasing thermogenesis.
Here is how it works: the catecholamines norepinephrine and epinephrine act as regulators of glycogen catabolism and liploysis. They are released in response to fright, exercise, stress, cold, etc; they are part of a coordinated response to prepare an individual for emergencies and are often referred to as the "fight or flight" reactions. A release in catecholamines results in an increase in heart rate and, subsequently, thermogenesis; but this is a transient process, which is where EGCG comes into play.
The catecholamine norepinephrine is quickly hydrolyzed by a specific enzyme, catechol O-methyltransferase (COMT). However, it has been shown in vitro that green tea extract inhibits this enzyme, thereby allowing norepinephrine to be upregulated. This can be important because norepinephrine normally binds to the receptor and activates the enzyme adenylate cyclase.
When activated, this enzyme converts adenosine triphosphate (ATP) into cyclic-adenosine monophosphate (cAMP). cAMP activates hormone sensitive lipase (HSL), but is rapidly degraded to 5-adenosine monophosphate (5-AMP) via another enzyme, phosphodiesterase (PDE). Since HSL is important in breaking down triglyceride molecules, it would be ideal for cAMP to be preferentially shuttled to HSL, rather than being hydrolyzed.
Subsequently, green tea catecholamines allow the first part of this reaction to occur and prolong the thermogenic process. However, this process will ultimately come to an end as well; cAMP is also quickly hydrolyzed to 5-AMP rather than continuing on its path to activating HSL. Here's where caffeine comes into play. It is well established that caffeine can inhibit PDE and allow cAMP to continue its job as a "second messenger" allowing for the enzyme HSL to break down triglycerides and prolong the thermogenic process.
A study published in 1999 demonstrated that green tea does in fact increase metabolic rate. In this particular study, research gave subjects one of three supplements: green tea extract (providing a total of 270 mg EGCG plus 150 mg caffeine per day), 150 mg caffeine per day, or a placebo.
The caffeine only group was put in place to determine if the EGCG had any additive effect to the known ergogenic benefits of caffeine.
After the short, 24-hour study, researchers noted a significant increase in resting metabolic rate (4%) in the EGCG + caffeine group vs. the caffeine or placebo groups. While this did not correlate to a decrease in bodyweight, it was only a one day study. Therefore, longer term research is necessary to determine if the body would grow accustomed to this stimulant, or if this increase in metabolic rate would continue for the duration of supplementation, which could obviously enhance weight loss.
There have been several other papers and abstracts published using products that contain green tea, but they are typically combined with other ingredients making it difficult to tease out the effects of green tea.
At this time it appears that green tea extract is safe, but again, longer studies need to be conducted to truly assess the efficacy of this supplement on weight management. Keep in mind that one cup of brewed green tea supplies approximately 50-100 mg of EGCG.
However, this value is dependent on temperature of the water, type of leaf, season of cultivation, etc. However, since there is also research to support the notion that tea consumption as a beverage is correlated to lower bodyweight, coupled with the known health benefits of green tea, if there are no known contraindications, such as use of coumadin, regular consumption is a wise idea.
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