tl, dr: Is green tea for weight loss? | Biokompost
It is suspected that green tea increases metabolism due to the high content of caffeine and catechins (about five times as much as in black tea). These substances the chew are lead to increased metabolic rate and increased energy expenditure of the body. Is this true?
Yes: it is known that green tea increases thermogenesis - which in itself is not very special, because similar effects have coffee and various spices (Westerp-Plantenga 2006). Caffeine affects thermogenesis probably affecting the metabolism particles called cAMP, which is very important in the regulation of metabolism. In addition, caffeine is likely to reduce appetite. On the other hand, catechins contained in green tea (black they do not exist due to the fermentation process used to obtain black tea, green tea) can serve as inhibitors of certain enzyme, which inter alia breaks down norepinephrine, which also has an impact on the rate of metabolism.
In addition, the thermogenic effect of green tea is stronger than the effect of drinking similar amounts of coffee or black tea, just because it contains in addition to caffeine also these mysterious catechins. And increased the chew thermogenesis is increased energy expenditure. So that we know about how green tea has to work.
Well all this fajno, very beautiful functional explanation, but whether green tea has a real impact on the effectiveness of weight loss or diet? It is not enough the chew to point to a mechanism must also check whether it works in practice, preferably by means of clinical research.
P IEC years ago Hursel and colleagues summarized the results of the eleven previous work. In these 11 works were fifteen comparisons (because some jobs have compared more than one group of people). This summary is called a meta-analysis and provides typically the most robust, reliable results. the chew
Among the works analyzed were those that showed the existence of a significant effect of green tea (GT) and such that no effect the chew is not stated. Taken into account both the work that explored the impact of GT on weight loss and long-term maintenance of low weight. In all the work of the low-energy diet was used (e.g., 500 kcal per day) in two groups of people: those who consumed additionally GT, and those which do not consumed (or used the placebo). So not asked about whether to lose weight from GT or GT only helps chudnięciu.
The total effect of green tea was modest, but it was. People who drank green tea, chudły an average of 1.3 kg more, or - after the diet - weight gain of 1.3 kg less than those who do not use green tea (95% confidence interval 0.6-2 kg, p <0.0001). It's not much, considering that the studies recruited people with very overweight or obese.
The following illustration is typical for meta-analysis. Each row, except the last one corresponds to a comparison of fifteen taken into account. Black box shows the estimated effect size in the comparison, and the handles on both sides of the square that - confidence intervals. The confidence intervals show us how much we can trust the estimation of the effect; For example, if overlapping vertical dashed line represents no effect, this effect is not statistically significant (*).
N Unfortunately, there are bad news (for some), what you see besides the illustration above. Probably drinking coffee (**) reduces the effectiveness of green tea to the extent that the effect may completely disappear. This is probably the case that if you drink on a daily basis a lot of coffee, it already enjoys with the thermogenic effects of caffeine, the chew and adding more green tea does not have much impact the chew on the results of the diet. Note that only three works above were examined people regularly consuming the chew caffeine, and none of these comparisons effect was not statistically significant. In contrast, no one called, what would happen if a lot of coffee drinkers or black tea and green tea have replaced it.
The work that I have chosen for this article is not the only one. The results of the meta-analyzes of other, however, were reasonably similar. Phung et al. (2010) found that the effect of catechins from green tea is statistically significant, but small. In another analysis (Jurgens et al. 2012) the total effect was even smaller, and most analyzes statistically insignificant.
(*) The confidence interval can be interpreted as follows: if a lifetime I will count 95% confidence intervals of these, in 5% of cases the true (not estimated) effect size will be numbered, or reckoned lay outside the chew the confidence interval. It is sometimes said that "there is a 95% probability that the true effect lies in the 95% confidence interval," but strictly speaking, from a statistical point of view, this is not the correct wording.
Hursel, R., Viechtbauer, W., & WESTERTERP-Plantenga, M. (2009). The effects of green tea on weight loss and weight maintenance: a meta-analysis In
It is suspected that green tea increases metabolism due to the high content of caffeine and catechins (about five times as much as in black tea). These substances the chew are lead to increased metabolic rate and increased energy expenditure of the body. Is this true?
Yes: it is known that green tea increases thermogenesis - which in itself is not very special, because similar effects have coffee and various spices (Westerp-Plantenga 2006). Caffeine affects thermogenesis probably affecting the metabolism particles called cAMP, which is very important in the regulation of metabolism. In addition, caffeine is likely to reduce appetite. On the other hand, catechins contained in green tea (black they do not exist due to the fermentation process used to obtain black tea, green tea) can serve as inhibitors of certain enzyme, which inter alia breaks down norepinephrine, which also has an impact on the rate of metabolism.
In addition, the thermogenic effect of green tea is stronger than the effect of drinking similar amounts of coffee or black tea, just because it contains in addition to caffeine also these mysterious catechins. And increased the chew thermogenesis is increased energy expenditure. So that we know about how green tea has to work.
Well all this fajno, very beautiful functional explanation, but whether green tea has a real impact on the effectiveness of weight loss or diet? It is not enough the chew to point to a mechanism must also check whether it works in practice, preferably by means of clinical research.
P IEC years ago Hursel and colleagues summarized the results of the eleven previous work. In these 11 works were fifteen comparisons (because some jobs have compared more than one group of people). This summary is called a meta-analysis and provides typically the most robust, reliable results. the chew
Among the works analyzed were those that showed the existence of a significant effect of green tea (GT) and such that no effect the chew is not stated. Taken into account both the work that explored the impact of GT on weight loss and long-term maintenance of low weight. In all the work of the low-energy diet was used (e.g., 500 kcal per day) in two groups of people: those who consumed additionally GT, and those which do not consumed (or used the placebo). So not asked about whether to lose weight from GT or GT only helps chudnięciu.
The total effect of green tea was modest, but it was. People who drank green tea, chudły an average of 1.3 kg more, or - after the diet - weight gain of 1.3 kg less than those who do not use green tea (95% confidence interval 0.6-2 kg, p <0.0001). It's not much, considering that the studies recruited people with very overweight or obese.
The following illustration is typical for meta-analysis. Each row, except the last one corresponds to a comparison of fifteen taken into account. Black box shows the estimated effect size in the comparison, and the handles on both sides of the square that - confidence intervals. The confidence intervals show us how much we can trust the estimation of the effect; For example, if overlapping vertical dashed line represents no effect, this effect is not statistically significant (*).
N Unfortunately, there are bad news (for some), what you see besides the illustration above. Probably drinking coffee (**) reduces the effectiveness of green tea to the extent that the effect may completely disappear. This is probably the case that if you drink on a daily basis a lot of coffee, it already enjoys with the thermogenic effects of caffeine, the chew and adding more green tea does not have much impact the chew on the results of the diet. Note that only three works above were examined people regularly consuming the chew caffeine, and none of these comparisons effect was not statistically significant. In contrast, no one called, what would happen if a lot of coffee drinkers or black tea and green tea have replaced it.
The work that I have chosen for this article is not the only one. The results of the meta-analyzes of other, however, were reasonably similar. Phung et al. (2010) found that the effect of catechins from green tea is statistically significant, but small. In another analysis (Jurgens et al. 2012) the total effect was even smaller, and most analyzes statistically insignificant.
(*) The confidence interval can be interpreted as follows: if a lifetime I will count 95% confidence intervals of these, in 5% of cases the true (not estimated) effect size will be numbered, or reckoned lay outside the chew the confidence interval. It is sometimes said that "there is a 95% probability that the true effect lies in the 95% confidence interval," but strictly speaking, from a statistical point of view, this is not the correct wording.
Hursel, R., Viechtbauer, W., & WESTERTERP-Plantenga, M. (2009). The effects of green tea on weight loss and weight maintenance: a meta-analysis In
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