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Green Tea and Reduction in weight
Abstract
Obesity is a growing epidemiological concern throughout the world. Many people are seeking
help from alternative medicines or natural remedies to solve this problem. Green tea has been
widely studied by researchers to confirm its possible positive health effects. Many studies
reported that green tea catechins’ (GTCs) consumption could prove to be helpful in lowering
down the BMI, body fat as well as body weight. The purpose of this paper is to review several
clinical interventions and epidemiological studies to investigate and confirm the effect of green
tea on weight loss.
Pub med was searched for English language studies that reported the long term effects of
catechins on weight loss, weight maintenance, and body fat. Seven relevant articles within the
last 10 years were considered. In addition, due to the limited number of epidemiological
researches on the impact(s) of green tea regarding weight loss, studies that examined catechins
from sources excluding green tea were also taken.
Results of clinical intervention studies are inconsistent. It appears that green tea produces better
results in combination with caffeine, in the Asian population, and on overweight but not obese
subjects. Caffeine, ethnicity, and BMI could be potential elements affecting results of green tea
catechins on weight loss. Though, recommendation regarding consumption of green tea to
obtain the possible health benefits can be made but not specifically for weight loss. Therefore;
additional studies are required to verify the possible positive outcome of green tea on weight
loss.
Introduction:
Obesity is a growing epidemiological concern throughout the world. According to the center of
disease control and prevention website, 35.7% of the United States’ adults are obese. [1] There
are many causes for obesity out of which, the major factor causing weight gain is the high dietary
intake with low energy expenditure. Increased energy expenditure or decreased dietary intake
can help in reduction of body weight. [2]
Many people are seeking assistance from alternative medicines or natural remedies to reduce
their weight. Green tea has been widely studied by researchers to confirm its possible positive
health effects. Many studies reported that green tea catechins’ (GTCs) consumption can prove to
be helpful in lowering down the BMI, body fat as well as body weight and according to these,
the risk of cardiovascular disease and diabetes mellitus may also get reduced via its intake. [3]
Green tea contains phytochemicals called polyphenols. Major Polyphenols that are present in
green tea are known as; catechins which are of four types mainly: epicatechin (EC), epicatechin
gallate (ECG), epigallocatechin (EGC), and epigallocatechin gallate (EGCG) [2]. EGCG
epigallocatechin gallate is considered as the most pharmacologically active and most available
catechin in green tea and constitutes 50-80% of the total content of catechin in maximum
products that are produced via green tea. [4]
It has been reported that a 250 ml. green tea beverage contains an average of 50–100 mg.
catechins and 30–40 mg caffeine. In addition, it could also be suggested that caffeine may lead a
person towards weight loss via increment in energy expenditure. Therefore most studies
investigating the impact introduced via green tea on weight loss are also analyzing the
consequence of caffeine on weight loss as well. [4]
Many studies have observed the possible mechanisms that could probably explain the reason
why green tea catechins may cause weight loss. The proposed mechanisms by which green tea
catechins may reduce the weight include increased energy expenditure, increased fat oxidation,
reduced nutrients absorption, and reduced appetite. [4]
It has been described that owing to catechins’ presence in green tea, energy expenditure may
increase as these suppress catechol-o-methyl-transferase, the enzyme that corrupts non-
epinephrine therefore, may extend the effects of non- epinephrine which can result in increment
in energy spending and oxidation of fat.
Moreover, caffeine can also intensify this effect by suppressing phosphodiesterase, the enzyme
that degrades cyclic adenosine monophosphate (cAMP) which is released in response to non-
epinephrine. In addition, the increased energy expenditure by green tea consumption has been
observed in many human studies however, the increased fat oxidation showed mixed results and
the mechanism is not fully understood yet. [4]
It has also been observed that catechins can decrease nutrients’ absorption and reduce appetite.
Animal studies reported that green tea catechins may diminish nutrients’ absorption via
interfering with fat digestion by suppressing gastric and pancreatic lipase. Furthermore, in vitro
and cellular studies have reported that green tea catechins may decrease nutrients’ absorption via
interfering with glucose absorption by suppressing amylase and glucosidease functions. In
addition, it has been suggested in animal studies that green tea catechins reduce appetite by
increasing fat oxidation which can produce more ATPs that may inactivate the appetite receptors
and thus; could result in reduced appetite; more evidences are needed to support this effect. [4]
The purpose of this paper is to review several clinical interventions and epidemiological studies
to investigate and confirm the effect of green tea on weight loss. Moreover, many potential
confounders such as ethnicity and caffeine consumption may affect the results of these studies
which will also be addressed in this paper. Whether green tea can be recommend as a weight loss
supplement for the general public or not this would be addressed in future studies.
Methods:
Pub med was searched for English language studies that reported the long term effects of
catechins on; weight loss, weight maintenance, and body fat. Studies based on analysis of long
term effects of catechins which were performed for more than 90 days were selected. 7 relevant
articles within the last 10 years were considered. In addition, due to the limited amount of
epidemiological studies regarding the impact posed via green tea on weight of consumer, studies
that examined catechins from sources supplementary to green tea were also included.
Discussion:
Habitual green tea intake and weight loss study:
Unfortunately, epidemiological studies that could examine the consequence of green tea
catechins on body weight and weight loss are limited.
In Taiwan, a cross-sectional epidemiological study (published in 2003) observed the
consequence (s) of habitual tea intake on change in body fat in humans. The study enrolled
1103 adults, 569 men and 641 women, and used structured questionnaires to obtain information
about tea consumption and regarding lifestyle too. The study concluded that usual tea consumers
who consume tea once in a week (minimum) for 6 months and consumed tea for more than 10
years were lucky enough to have low body fat (reduced upto19.6%) and waist to hip ratio
(reduced up to 2.1%) in comparison to non-habitual consumers. This study proposed that
habitual green tea catechins’ consumption may help in weight loss. [5]
Green tea and weight maintenance study:
A weight maintenance cohort study which was conducted in Netherlands (and recruited 4280
adults) reported a relationship between catechin intake and weight maintenance as well as
changes in BMI over the study period. The study used food frequency questionnaires to assess
the dietary flavonols, flavones, and catechins consumption. In fact, the major...