ArticlePDF Available

Green Tea and Weight Loss: An update (Meta-Analysis)



Obesity is the growing health disorder globally and lifestyle changes are at the heart of this problem. It has been found that green tea market is increasing. One of the supposedly many effects of green tea is the weight loss. There is vast literature available related to this subject. The purpose of this study was to elucidate by meta-analysis whether green tea has an effect on body weight. PubMed search was done for the term - Green tea and later limited by English-language, human studies published in last decade and available as full text. Out of the 704 initially retrieved articles 11 were included in the present meta-analysis after considering the exclusion and inclusion criteria of the study. The pooled results of all the studies with the random effect model is -1.26 [-1.87 to -0.65]. It is imperative by this meta-analysis that green tea consumption leads to weight loss. However the substantial heterogeneity (I2 = 81.71%) among the studies warranties larger studies for confirmation and validation of the effect of green tea on weight of an individual.
International Journal of Biotechnology and Biomedical Sciences
Volume 1, Number 1; July- December, 2015 pp. 21-24
© Krishi Sanskriti Publications
Green Tea and Weight Loss:
An update (Meta-Analysis)
Poonam Pawar
Sir H N Medical Research society, Sir H N Reliance Foundation Hospital and Research Centre
Abstract—Obesity is the growing health disorder globally and
lifestyle changes are at the heart of this problem. It has been found
that green tea market is increasing. One of the supposedly many
effects of green tea is the weight loss. There is vast literature
available related to this subject. The purpose of this study was to
elucidate by meta-analysis whether green tea has an effect on body
weight. PubMed search was done for the term - Green tea and later
limited by English-language, human studies published in last decade
and available as full text. Out of the 704 initially retrieved articles 11
were included in the present meta-analysis after considering the
exclusion and inclusion criteria of the study. The pooled results of all
the studies with the random effect model is -1.26 [-1.87 to -0.65]. It is
imperative by this meta-analysis that green tea consumption leads to
weight loss. However the substantial heterogeneity (I2 = 81.71%)
among the studies warranties larger studies for confirmation and
validation of the effect of green tea on weight of an individual.
Keywords: Green Tea, Weight Loss, Meta-Analysis
Obesity is a growing health issue worldwide. According to
world health organization (WHO) report updated in January
2015 (a) prevalence of obesity has more than doubled since
1980 (b) 600 million adults are obese and 39% are overweight
as per the 2014 statistics (c) obesity is also prevalent in
children under age 5, according to 2013 statistics it accounts to
42 million [1].
Specifically in India there is a growing prevalence of obesity.
India is third most obese country in the world, just behind US
and China [2]. India is a developing country with 270 million
people under poverty line. In such a scenario the rise in
obesity and obesity related disorders focuses on the increasing
effect of Lifestyle changes specifically eating habits i.e. more
consumption of junk food [3].
The solution to this problem is to have healthy lifestyle
speaking of which opens a lot of doors from exercise to food.
India is the world’s largest Tea-drinking nation and there is an
emerging trend of drinking green tea is observed specifically
for the reasons of weight loss [4]. There is increase in the
demand of green tea in Indian market [5].
Asians have been aware of health benefits of green tea for
over a century [6] and for almost 24 years now, it is has been
considered as enhancer of energy expenditure and fat
oxidation and thereby inducing weight loss (WL) [7,8]. The
polyphenols in green tea such as EpiGalloCatechin Gallate
(EGCG) stimulates energy expenditure because it has
thermogenic effect as proven by a couple of short-term studies
showing significant increase in energy expenditure and fat
oxidation [9, 10]. Later on the longer term studies were
published on the effect from an EGCG–caffeine mixture on
Hence a lot of literature is generated in context to green tea
and weight loss. Therefore this study aimed to find out
whether green tea has effect on body weight through meta-
analysis of the available literature.
2.1 Identification of Relevant Studies
PubMed was searched for the term – Green tea.
The search was limited to English language and human
studies. All the studies available as free full text articles for
the past decade.
2.2 Inclusion and exclusion criteria
A study was included in the review if (a) the study participants
were randomly assigned to conditions, (b) the results allowed
a direct comparison of the effects of green tea consumption
(either dosage versus placebo or high dosage versus low
dosage) on either WL or WM, and (c) the study lasted at least
for 8 weeks. Green tea is served as either regular tea or as
An important exclusion criterion was the use of any tea other
than an EGCG–caffeine mixture (such as oolong tea).
2.3 Data extraction
We extracted data for various parameters from the original
articles using a standardized data extraction form. Wherein the
study’s author(s), year of publication, the duration of the
Poonam Pawar
International Journal of Biotechnology and Biomedical Sciences
Volume 1, Number 1; July- December, 2015
treatment phase (weeks), the age range, average body weight
and gender of the participants in the study was recorded. We
also recorded the number of participants and the dosage of
green tea administered (mg/day).
For each condition, we calculated or extracted the mean
weight change (kg) between the post-treatment and the
baseline assessment. For studies which mentioned WL and/or
WM the baseline corresponded to the time immediately before
starting of WL phase and /or WM phase respectively. The
post-treatment mean was recorded just after the intervention
ends. Irrespective of the study design, negative values for the
mean change, indicate WL, a value of zero indicates no
change, and positive values indicate an increase in the body
weight on average. The effect size measure for the
Metaanalysis was therefore difference between values of the
mean change for the treatment minus the mean change value
for the control group.
2.4 Statistical Analysis
The results are represented as weighted mean of the body
weights (kg) of the study participants. The Meta-Analysis is
performed using Exploratory Software for Confidence
Intervals, ESCI software. The effect size estimates were
aggregated based on a random effects model to estimate the
amount of heterogeneity in the effect sizes. We report the
estimated average effect (µ), the estimated amount of
heterogeneity (τ), and the estimated percentage of the total
amount of variability that can be attributed to heterogeneity
(I2). Corresponding 95% confidence intervals are given for all
of these statistics.
Initially 48 potentially relevant articles were retrieved.
These articles where then assessed on the basis of titles and
abstract thereby excluding in vitro studies, unrelated studies,
biochemical and molecular biology based studies..
Further review articles which didn’t contribute any additional
data were excluded. Also articles having any of the following
insufficiencies: 1) animal studies 2) full text in language other
than English 3) insufficient data; were excluded. The relevant
data from two studies was requested from the corresponding
authors through e-mail but could not be procured. Hence these
two studies could not be included in this review. None of these
studies were excluded due to lack of blinding. After this
rigorous screening, 10 articles are included in this review [13-
22]. Fig. 1 summarizes the selection procedure of these
More than one effect size could be calculate from two studies.
Hursel et al. [14] provided two effect sizes corresponding to
two sub-groups viz. adequate protein (AP) diet and high-
protein (HP) diet under green tea-caffeine mixture
consumption and placebo groups in WL and later WM. Also
Wang et al. [15] study group provided three effect size
estimates as a result of three treatment groups wherein
participants received increasing order of dosage as a result of
different number of servings. Therefore a total of 13 effect
size estimates could be extracted from the 9 studies. Fig. 2
shows a forest plot of the individual effect size estimates with
corresponding study weightings and 95% confidence intervals.
The random-effects model indicated a modest, but significant
positive effect of catechins on WL (µ = -1.26, 95% CI: -1.87
to -0.65; p = 0.01). Therefore, it is estimated that subjects in
the treatment groups lost on average 1.26 kg more weight (or
gained on average 1.26 kg less weight) than people in the
control groups [Fig. 2].
Removal of any individual study from the meta-analysis did
not alter this conclusion. However, the results were clearly
heterogeneous (I2 = 99.53%, p= 0.01; τ = 1.061 kg, 95% CI:
0.98, 1.15).
This meta-analysis shows green tea consumption has a
negative impact of body weight of an individual even when
consumed as an EGCG-caffeine mixture. Also the results
show that difference in dosage of catechins in the EGCG–
caffeine mixture among treatment and control groups had no
effect on overall effect size estimates of this meta-analysis.
Green Tea and Weight Loss: An update (Meta-Analysis) 23
International Journal of Biotechnology and Biomedical Sciences
Volume 1, Number 1; July- December, 2015
This result is in line with study by Berube-Parent et al. [10]
wherein different mixtures of EGCG and caffeine with a
different dosage of catechins were examined. The results from
that study showed that all mixtures increased 24-h energy
expenditure and that the increase was similar for all doses of
EGCG in the mixtures, which was also found in the study
from Wang et al. [15].
It is important to note all the studies included in this particular
meta-analysis had comparable designs: in the WL studies [13–
22] participants immediately started to consume an EGCG–
caffeine mixture for 8-12 weeks following randomization. All
studies had test period for at least 12-13 weeks except for
Tsuchida T et al. [21] that had a test period of 8 weeks. Two
WM studies [14, 20] had participants with first weight loss
phase for 4 weeks using a very low energy diet, followed by
randomization and then an EGCG–caffeine mixture
supplementation phase for either 12 or 13 weeks. One study
[16] randomly assigned subjects to three different dosage
conditions as compared to controls. All the studies had true
placebo group except one [22] made the comparison between
two groups of low and high dosage of catechins.
However there was significant heterogeneity observed in this
meta-analysis. Therefore there was a need to look up for
factors influencing meta-analytical heterogeneity. Two factors
were highlighted from the data provided in the research
articles included in this review which are ethnicity and
habitual caffeine intake. It is noted that Asian studies had a
low caffeine intake and while almost all Caucasian studies had
a high caffeine intake. Although caffeine intake was not a
significant moderator alone but when examined together in a
model including ethnicity it was found have an impact. If
more studies with both ethnicities with different amounts of
caffeine intake are conducted and then a similar meta-analysis
would provide a clearer picture of the effectiveness of these
Taken together, this meta-analysis has shown that EGCG–
caffeine mixtures have a positive effect on WL and on WM.
Moreover, it also shows that habitual caffeine intake and
ethnicity may be moderators, whereas different doses of
catechins do not have a significantly different effect.
Medical Research Society of Sir H N Reliance Foundation
Hospital and Research Centre for providing necessary
infrastructure for this review writing.
[1] "Obesity and Overweight." WHO. N.p., Jan. 2015. Web. 30 May
[2] Ng, Marie et al. Global, regional, and national prevalence of
overweight and obesity in children and adults during 1980–
2013: a systematic analysis for the Global Burden of Disease
Study 2013. The Lancet , Volume 384 , Issue 9945 , 766 - 781
[3] "India the Third Most Obese Country in the World.” Mail Today,
News. N.p., n.d. Web. 27 May 2015.
[4] Jane Pettigrew, The Tea Companion, Running Press, 2004.
[5] "Green Tea Market to Touch Rs 400 Crore in FY'15: Tata
Global." Timesofindia-economictimes. N.p., n.d. Web. 27 May
[6] Shixian Q, VanCrey B, Shi J, Kakuda Y, Jiang Y. Green tea
extract thermogenesis-induced weight loss by epigallocatechin
gallate inhibition of catechol-O-methyltransferase. J Med Food
2006; 9: 451–458.
[7] Westerterp-Plantenga M, Diepvens K, Joosen AM, Berube-
Parent S, Tremblay A. Metabolic effects of spices, teas, and
caffeine. Physiol Behav 2006; 89: 85–91.
[8] Diepvens K, Westerterp KR, Westerterp-Plantenga MS. Obesity
and thermogenesis related to the consumption of caffeine,
ephedrine, capsaicin, and green tea. Am J Physiol Regul Integr
Comp Physiol 2007; 292: R77–R85
[9] Dulloo AG, Duret C, Rohrer D, Girardier L, Mensi N, Fathi M
et al. Efficacy of a green tea extract rich in catechin polyphenols
and caffeine in increasing 24-h energy expenditure and fat
oxidation in humans. Am J Clin Nutr 1999; 70: 1040–1045.
[10] Berube-Parent S, Pelletier C, Dore J, Tremblay A. Effects of
encapsulated green tea and Guarana extracts containing a
mixture of epigallocatechin-3-gallate and caffeine on 24 h
energy expenditure and fat oxidation in men. Br J Nutr 2005; 94:
[11] Maki, K. C., M. S. Reeves, M. Farmer, K. Yasunaga, N. Matsuo,
Y. Katsuragi, M. Komikado, I. Tokimitsu, D. Wilder, F. Jones, J.
B. Blumberg, and Y. Cartwright. Green Tea Catechin
Consumption Enhances Exercise-Induced Abdominal Fat Loss
in Overweight and Obese Adults. J Nutr. 2009 Feb; 139(2):264-
[12] Brown, A. Louise, Joan Lane, Jacqueline Coverly, Janice Stocks,
Sarah Jackson, Alison Stephen, Les Bluck, Andy Coward, and
Hilde Hendrickx. Effects of Dietary Supplementation with the
Green Tea Polyphenol Epigallocatechin-3-gallate on Insulin
Resistance and Associated Metabolic Risk Factors: Randomized
Controlled Trial. Br J Nutr. 2009 March; 101(6): 886–894.
[13] Hsu CH1, Liao YL, Lin SC, Tsai TH, Huang CJ, Chou P. Does
supplementation with green tea extract improve insulin
resistance in obese type 2 diabetics? A randomized, double-
blind, and placebo-controlled clinical trial. Altern Med Rev.
2011 Jun;16(2):157-63. J Nutr.
[14] Hursel R, and MS Westerterp-Plantenga. "Green Tea Catechin
plus Caffeine Supplementation to a High-protein Diet Has No
Additional Effect on Body Weight Maintenance after Weight
Loss." Am J Clin Nutr.89.3 (2009): 822-30.
[15] Wang M, Wen Y, Du Y, Yan X, Wei Guo H, Rycroft J et al. The
effects of 90 days consumption of a high-catechin green tea
beverage on body weight. Eur J Clin Nutr 2008.
[16] Auvichayapat P, Prapochanung M, Tunkamnerdthai O,
Sripanidkulchai BO, Auvichayapat N, Thinkhamrop B et al.
Effectiveness of green tea on weight reduction in obese Thais: a
randomized, controlled trial. Physiol Behav 2008; 93: 486–491.
[17] Hsu CH, Tsai TH, Kao YH, Hwang KC, Tseng TY, Chou P.
Effect of green tea extract on obese women: a randomized,
double-blind, placebo-controlled clinical trial. Clin Nutr 2008;
27: 363–370.
Poonam Pawar
International Journal of Biotechnology and Biomedical Sciences
Volume 1, Number 1; July- December, 2015
[18] Nagao T, Hase T, Tokimitsu I. A green tea extract high in
catechins reduces body fat and cardiovascular risks in humans.
Obesity (Silver Spring) 2007; 15: 1473–1483.
[19] Diepvens K, Kovacs EM, Nijs IM, Vogels N, Westerterp-
Plantenga MS. Effect of green tea on resting energy expenditure
and substrate oxidation during weight loss in overweight
females. Br J Nutr 2005; 94: 1026–1034.
[20] Kovacs EM, Lejeune MP, Nijs I, Westerterp-Plantenga MS.
Effects of green tea on weight maintenance after body-weight
loss. Br J Nutr 2004; 91: 431–437.
[21] Tsuchida T, Itakura H, Nakamura H. Reduction of body fat in
humans by long-term ingestion of catechins. Prog Med 2002;
22: 2189–2203.
[22] Hase T, Komine Y, Meguro S, Takeda Y, Takahashi H, Matsui Y
et al. Anti-obesity effects of tea catechins in humans. J Oleo Sci
2001; 50: 599–605.
... Several studies have suggested that the flavonoids and caffeine in green tea can help elevate metabolic rate, increase fat oxidation and even improve insulin activity. Consumption of green tea and caffeine helps to lose an average of 2.9 pounds during a 12-week period, while sticking to regular diet and increase in calorie output was equal to about 100 calories over a 24-hour period [10]. Tea is also known to lower the risk of heart disease, stress relief, fat reduction and weight loss [11]. ...
... The phosphomolybdenum reagent was prepared by using 3.33 mL of concentrated sulfuric acid (0.6M) in 100 mL water, 0.335g (10,20,40 and 80 µg/mL) was used as a positive control for calculating the total antioxidant activity. From each extract/standard 0.2 mL was taken in a test tube and to this was added 2 mL of phosphomolybdenum reagent and 1.8 mL of water. ...
... Black tea (Lipton ® ) 10.46 ...
Full-text available
The aim of the present work was to quantify caffeine and total phenolic content and to evaluate the antioxidant activity in commercially available black tea, green tea, Turkish coffee and traditional Omani qahwa. Aqueous extracts of tea and coffee samples prepared by decoction were subjected to the phytochemical screening test for phenols and caffeine. Caffeine in the samples was quantified with the help of a linear regression equation obtained from the standard plot. Total phenolic and flavonoid contents in the tea and coffee were estimated colorimetrically. Antioxidant activity of the samples was investigated by DPPH (1, 1 diphenyl picrylhydrazyl) free radical assay and phosphomolybdenum methods. All the test extracts showed the presence of phenolic compounds and caffeine. The results indicated a variation in caffeine content, phenolic content, flavonoid content and antioxidant activity between the two extracts and among same extracts with different brand names. In general, Mumtaz black tea was found to contain the highest caffeine (24.44 mg/g) and phenolic content (8.27 mg/g of GAE). It also showed the highest total antioxidant activity (10.46 mg/g of ascorbic acid equivalent) but surprisingly its flavonoid content and antioxidant activity by DPPH method was lower than other samples. Tea was found to be richer in phenols and caffeine but Omani qahwa showed better antioxidant activity. It can be concluded that phenolic content and the antioxidant activities depend on the origin, brands and additives of these beverages that may lead to variation in the content and bioactivity.
... The outcomes obtained from the meta-analysis demonstrated that an EGCC-caffeine mixture affects WL and WM long after the negative balance of energy. Moreover, the interchange of ethnicity and habitual caffeine intake was shown a facilitator(Pawar, 2015;Hursel, 2009).Regarding the use of lemons in our study, it was concluded that 29.5% reduced weight in study participants and this was a similar finding with Negar et al., (2016), who found that group 1 had a substantial reduction in overall cholesterol (P =0.001), lowdensity lipoprotein-cholesterol (P =0.001), and fibrinogen (P =0.001), as compared to the other classes. Group 1, with respect to groups 3 and 4 (37 ± 10, P = 0.01) (24 ± 1, P = 0.02), a larger decrease in the systolic and diastolic blood pressure was observed respectively; Additionally, the combined group has a significant decrease in body mass index as compared to the lemon juice and control groups (P = 0.04). ...
Full-text available
Background: Obesity is a common and morbid disease. There are different methods to reduce weight. The most common surgical methods to reduce weight are bariatric surgical procedures which include gastric bypass, adjustable gastric banding and sleeve gastrectomy. Many drugs have been developed for the long-term management of obesity to cause a positive energy balance. Some herbal medicine products are taken as liquids or tea prior to eating, such as chamomile, green tea can assist in reducing weight. Others spices such as ginger help in weight loss. Many researches suggest that exercise is more effective in the prevention of overweight and obesity than its reversal. The aim of this study is to compare the use of surgery, drugs, exercise, and focusing on herbal remedies regarding weight reduction and to help in raising awareness among people to maintain healthy lifestyle. Method: A Cross-sectional study has been done among people in Ha'il, KSA. The data are collected by distributing online questionnaire. Statistical analysis has been done with (SPSS) V 23.0 (Chi-Square Tests considering level of significance P≤ 0.001 and P≤ 0.05). Result: The result of this study showed that a total 552 of participants in Hail, 29 (6.4%) female and 2 (2.2%) male had used herbs to reduce their weight and the most common used herbs were green tea, lemon, ginger and cinnamon respectively. 21 participants (4.6%) of female and 5 (5.6%) of male prefer surgery for weight loss. The 166 (36.4%) of female, while the male 36 (40.4%) make use of exercise to reduce the weight. Also, 3 (0.7%) of female used the drug, while male never used. Conclusion: The study concluded that the most common method used was exercise. The others were herbs, surgery and drugs, respectively.
... Srinivas et al observed in his study 31.5% skip meals as a weight control measure.18 With same method of consuming green tea for weight reduction practices a study done by Pawar et al showed positive result in weight reduction and weight maintenance.19 ...
Full-text available
Background: Worldwide obesity prevalence has nearly doubled since 1980. Current guidelines recommend that “overweight” and “obese” individuals lose weight through engaging in lifestyle modification involving diet, exercise and other behaviour changes. It is necessary to prevent obesity so that the subsequent complications can be prevented.Methods: This community based cross sectional study was conducted in the field practice area of tertiary medical college from June 2019 to August 2019. Totally 154 participants enrolled in the study. Only those individuals who had body mass index (BMI) of more than 23 kg/m2 were included in the study.Results: Majority of the study subjects 57.1% (88) belonged to the age group of 21-40 years. We included only overweight and obese adults in the present study. In this study, 61% (94) of the study population belonged to obese- I category while 33.8% (52) belonged to obese- II and only 5.2% (3) of study population were overweight. Only 43% (66) of the study population had adopted some measures to reduce their weight. Out of these majority 69.7% (46) preferred walking while 12.1% (8) preferred jogging for reducing weight. Mean days of walking adopted was 3.7 days and mean minutes per day was 29.67 minutes.Conclusions: As seen in this study more than half of the study population had not taken any measures for weight reduction. Increased health awareness will improve their level of active participation in the weight reduction program such as diet modification and physical exercise promotes weight loss and weight maintenance.
Full-text available
Background: In 2010, overweight and obesity were estimated to cause 3·4 million deaths, 3·9% of years of life lost, and 3·8% of disability-adjusted life-years (DALYs) worldwide. The rise in obesity has led to widespread calls for regular monitoring of changes in overweight and obesity prevalence in all populations. Comparable, up-to-date information about levels and trends is essential to quantify population health effects and to prompt decision makers to prioritise action. We estimate the global, regional, and national prevalence of overweight and obesity in children and adults during 1980-2013. Methods: We systematically identified surveys, reports, and published studies (n=1769) that included data for height and weight, both through physical measurements and self-reports. We used mixed effects linear regression to correct for bias in self-reports. We obtained data for prevalence of obesity and overweight by age, sex, country, and year (n=19,244) with a spatiotemporal Gaussian process regression model to estimate prevalence with 95% uncertainty intervals (UIs). Findings: Worldwide, the proportion of adults with a body-mass index (BMI) of 25 kg/m(2) or greater increased between 1980 and 2013 from 28·8% (95% UI 28·4-29·3) to 36·9% (36·3-37·4) in men, and from 29·8% (29·3-30·2) to 38·0% (37·5-38·5) in women. Prevalence has increased substantially in children and adolescents in developed countries; 23·8% (22·9-24·7) of boys and 22·6% (21·7-23·6) of girls were overweight or obese in 2013. The prevalence of overweight and obesity has also increased in children and adolescents in developing countries, from 8·1% (7·7-8·6) to 12·9% (12·3-13·5) in 2013 for boys and from 8·4% (8·1-8·8) to 13·4% (13·0-13·9) in girls. In adults, estimated prevalence of obesity exceeded 50% in men in Tonga and in women in Kuwait, Kiribati, Federated States of Micronesia, Libya, Qatar, Tonga, and Samoa. Since 2006, the increase in adult obesity in developed countries has slowed down. Interpretation: Because of the established health risks and substantial increases in prevalence, obesity has become a major global health challenge. Not only is obesity increasing, but no national success stories have been reported in the past 33 years. Urgent global action and leadership is needed to help countries to more effectively intervene. Funding: Bill & Melinda Gates Foundation.
Full-text available
This study evaluated the influence of a green tea catechin beverage on body composition and fat distribution in overweight and obese adults during exercise-induced weight loss. Participants (n = 132 with 107 completers) were randomly assigned to receive a beverage containing approximately 625 mg of catechins with 39 mg caffeine or a control beverage (39 mg caffeine, no catechins) for 12 wk. Participants were asked to maintain constant energy intake and engage in >or=180 min/wk moderate intensity exercise, including >or=3 supervised sessions per week. Body composition (dual X-ray absorptiometry), abdominal fat areas (computed tomography), and clinical laboratory tests were measured at baseline and wk 12. There was a trend (P = 0.079) toward greater loss of body weight in the catechin group compared with the control group; least squares mean (95% CI) changes, adjusted for baseline value, age, and sex, were -2.2 (-3.1, -1.3) and -1.0 (-1.9, -0.1) kg, respectively. Percentage changes in fat mass did not differ between the catechin [5.2 (-7.0, -3.4)] and control groups [-3.5 (-5.4, 1.6)] (P = 0.208). However, percentage changes in total abdominal fat area [-7.7 (-11.7, -3.8) vs. -0.3 (-4.4, 3.9); P = 0.013], subcutaneous abdominal fat area [-6.2 (-10.2, -2.2) vs. 0.8 (-3.3, 4.9); P = 0.019], and fasting serum triglycerides (TG) [-11.2 (-18.8, -3.6) vs. 1.9 (-5.9, 9.7); P = 0.023] were greater in the catechin group. These findings suggest that green tea catechin consumption enhances exercise-induced changes in abdominal fat and serum TG.
Full-text available
Animal evidence indicates that green tea may modulate insulin sensitivity, with epigallocatechin-3-gallate (EGCG) proposed as a likely health-promoting component. The purpose of this study was to investigate the effect of dietary supplementation with EGCG on insulin resistance and associated metabolic risk factors in man. Overweight or obese male subjects, aged 40-65 years, were randomly assigned to take 400 mg capsules of EGCG (n 46) or the placebo lactose (n 42), twice daily for 8 weeks. Oral glucose tolerance testing and measurement of metabolic risk factors (BMI, waist circumference, percentage body fat, blood pressure, total cholesterol, LDL-cholesterol, HDL-cholesterol, TAG) was conducted pre- and post-intervention. Mood was evaluated weekly using the University of Wales Institute of Science and Technology mood adjective checklist. EGCG treatment had no effect on insulin sensitivity, insulin secretion or glucose tolerance but did reduce diastolic blood pressure (mean change: placebo - 0.058 (se 0.75) mmHg; EGCG - 2.68 (se 0.72) mmHg; P = 0.014). No significant change in the other metabolic risk factors was observed. The EGCG group also reported feeling in a more positive mood than the placebo group across the intervention period (mean score for hedonic tone: EGCG, 29.11 (se 0.44); placebo, 27.84 (se 0.46); P = 0.048). In conclusion, regular intake of EGCG had no effect on insulin resistance but did result in a modest reduction in diastolic blood pressure. This antihypertensive effect may contribute to some of the cardiovascular benefits associated with habitual green tea consumption. EGCG treatment also had a positive effect on mood. Further studies are needed to confirm the findings and investigate their mechanistic basis.
Full-text available
The present study was conducted to investigate whether green tea may improve weight maintenance by preventing or limiting weight regain after weight loss of 5 to 10 % in overweight and moderately obese subjects. The study had a randomised, parallel, placebo-controlled design. A total of 104 overweight and moderately obese male and female subjects (age 18-60 years; BMI 25-35 kg/m(2)) participated. The study consisted of a very-low-energy diet intervention (VLED; 2.1 MJ/d) of 4 weeks followed by a weight-maintenance period of 13 weeks in which the subjects received green tea or placebo. The green tea contained caffeine (104 mg/d) and catechins (573 mg/d, of which 323 mg was epigallocatechin gallate). Subjects lost 6.4 (sd 1.9) kg or 7.5 (sd 2.2) % of their original body weight during the VLED (P<0.001). Body-weight regain was not significantly different between the green tea and the placebo group (30.5 (sd 61.8) % and 19.7 (sd 56.9) %, respectively). In the green tea treatment, habitual high caffeine consumption was associated with a higher weight regain compared with habitual low caffeine consumption (39 (sd 17) and 16 (sd 11) %, respectively; P<0.05). We conclude that weight maintenance after 7.5 % body-weight loss was not affected by green tea treatment and that habitual caffeine consumption affected weight maintenance in the green tea treatment.
We assessed the effect of ingestion of green tea (GT) extract along with a low-energy diet (LED) on resting energy expenditure (REE), substrate oxidation and body weight as GT has been shown to increase energy expenditure and fat oxidation in the short term in both animals and people. Forty-six overweight women (BMI 27 center dot 6 (sd 1 center dot 8) kg/m(2)) were fed in energy balance from day 1 to day 3, followed by a LED with GT (1125 mg tea catechins +225 mg caffeine/d) or placebo (PLAC) from day 4 to day 87. Caffeine intake was standardised to 300 mg/d. Energy expenditure was measured on days 4 and 32. Reductions in weight (4 center dot 19 (sd 2 center dot 0) kg PLAC, 4 center dot 21 (sd 2 center dot 7) kg GT), BMI, waist:hip ratio, fat mass and fat-free mass were not statistically different between treatments. REE as a function of fat-free mass and fat mass was significantly reduced over 32 d in the PLAC group (P < 0 center dot 05) but not in the GT group. Dietary restraint increased over time (P < 0 center dot 001) in both groups, whereas disinhibition and general hunger decreased (P < 0 center dot 05). The GT group became more hungry over time and less thirsty, and showed increased prospective food consumption compared with PLAC (P < 0 center dot 05). Taken together, the ingestion of GT along with a LED had no additional benefit for any measures of body weight or body composition. Although the decrease in REE as a function of fat-free mass and fat mass was not significant with GT treatment, whereas it was with PLAC treatment, no significant effect of treatment over time was seen, suggesting that a robust limitation of REE reduction during a LED was not achieved by GT.
To examine the anti-obesity effects of tea catechins in humans, a trial study using healthy male subjects (27-47 years). Comprising in equal number a low dose catechin (LDC) group (n=11) and high dose catechin (HDC) group (n=12). The groups were administered catechins at 118.5 mg and 483.0 mg a day for 12 weeks, respectively. At 4 and 12 weeks, effect evaluation was made based on change in weight, body mass index (BMI), waist circumference, body fat ratio and abdominal fat as determined by computed tomography (CT) and triacylglycerol, total cholesterol, free fatty acid, glucose, insulin and total plasminogen activator inhibitor-1 (PAI-1) in serum. In the HDC group, at 12 weeks, weight, BMI, waist circumference, body fat ratio, abdominal fat and total cholesterol, glucose, insulin, PAI-1 in serum were noted to have significantly decreased from values at 0 week. In the LDC group, only weight, BMI and insulin had changed. In the HDC group, BMI had decreased significantly in 25≤BMI subjects compared to 25>BMI subjects. In the 25≤BMI subjects, BMI decreased significantly more in the HDC group. Tea catechins are thus shown here for the first time to have the anti-obesity effects in humans.
Green tea is one of the most popular beverages in the world. It is believed to have beneficial effects in the prevention and treatment of many diseases, one of which is type 2 diabetes. The aim of the study is to examine the effect of a decaffeinated green tea extract (GTE) providing a daily dose of 856 mg of epigallocatechin gallate (EGCG) on obese individuals with type 2 diabetes. The clinical trial was a randomized, double-blind, placebo-controlled clinical trial conducted from December 2007 through November 2008. The subjects were randomly assigned to either receive 1,500 mg of a decaffeinated GTE or placebo daily for 16 weeks. Sixty-eight of 80 subjects, ages 20-65 years with BMI > 25 kg/m2 and type 2 diabetes for more than one year, completed this study. Homeostasis model assessment for insulin resistance (HOMA-IR) was used as the major outcome measurement. At baseline and after 16 weeks of treatment, anthropometric measurements, fasting glucose, hemoglobin A1C percent (HbA1C), hormone peptides, and plasma lipoproteins were measured from both groups. No statistically significant differences were detected between the decaffeinated GTE and placebo groups in any measured variable. A statistically significant within-group 0.4-percent reduction in HbA1C (from 8.4 to 8.0%) was observed after GTE treatment compared to baseline. Within-group comparison also revealed that the GTE group had significant reductions in waist circumference (WC), HOMA-IR index, and insulin level, and a significant increase in the level of ghrelin. Within-group comparison of those in the placebo group showed a significant increase in the level of ghrelin. This study found no statistical difference in any measured variable between the decaffeinated GTE and placebo groups; however, there were some statistically significant within-group changes detected. More research is required to determine whether a decaffeinated GTE standardized for EGCG content will provide any clinical benefits in obese individuals with type 2 diabetes. Clinical Trial Registration NO: NCT00567905.
Green tea (epigallocatechin gallate + caffeine) and protein each were shown to improve body weight maintenance after weight loss. We investigated the effect of a green tea-caffeine mixture added to a high-protein (HP) diet on weight maintenance (WM) after body weight loss in moderately obese subjects. A randomized, placebo-controlled, double-blind parallel trial was conducted in 80 overweight and moderately obese subjects [age (mean +/- SD): 44 +/- 2 y; body mass index (BMI; in kg/m(2)): 29.6 +/- 2.0] matched for sex, age, BMI, height, body mass, and with a habitually low caffeine intake. A very-low-energy diet intervention during 4 wk was followed by 3 mo of WM; during the WM period, the subjects received a green tea-caffeine mixture (270 mg epigallocatechin gallate + 150 mg caffeine/d) or placebo, both in addition to an adequate protein (AP) diet (50-60 g protein/d) or an HP diet (100-120 g protein/d). Subjects lost 7.0 +/- 1.6 kg, or 8.2 +/- 2.0%, body weight (P < 0.001). During the WM phase, WM, resting energy expenditure, and fat-free mass (FFM) increased relatively in both the HP groups and in the AP + green tea-caffeine mixture group (P < 0.05), whereas respiratory quotient and body fat mass decreased, all compared with the AP + placebo group. Satiety increased only in both HP groups (P < 0.05). The green tea-caffeine mixture was only effective with the AP diet. The green tea-caffeine mixture, as well as the HP diet, improved WM independently through thermogenesis, fat oxidation, sparing FFM, and, for the HP diet, satiety; a possible synergistic effect failed to appear.
Current interest in the role of functional foods in weight control has focused on plant ingredients capable of interfering with the sympathoadrenal system. We investigated whether a green tea extract, by virtue of its high content of caffeine and catechin polyphenols, could increase 24-h energy expenditure (EE) and fat oxidation in humans. Twenty-four-hour EE, the respiratory quotient (RQ), and the urinary excretion of nitrogen and catecholamines were measured in a respiratory chamber in 10 healthy men. On 3 separate occasions, subjects were randomly assigned among 3 treatments: green tea extract (50 mg caffeine and 90 mg epigallocatechin gallate), caffeine (50 mg), and placebo, which they ingested at breakfast, lunch, and dinner. Relative to placebo, treatment with the green tea extract resulted in a significant increase in 24-h EE (4%; P < 0.01) and a significant decrease in 24-h RQ (from 0.88 to 0.85; P < 0.001) without any change in urinary nitrogen. Twenty-four-hour urinary norepinephrine excretion was higher during treatment with the green tea extract than with the placebo (40%, P < 0.05). Treatment with caffeine in amounts equivalent to those found in the green tea extract had no effect on EE and RQ nor on urinary nitrogen or catecholamines. Green tea has thermogenic properties and promotes fat oxidation beyond that explained by its caffeine content per se. The green tea extract may play a role in the control of body composition via sympathetic activation of thermogenesis, fat oxidation, or both.