Effects of green tea on lipid metabolism in overweight or obese people

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Received: 12 26, 2016; Revised: 05 25, 2017; Accepted: 05 26, 2017 
 
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10.1002/mnfr.201601122 . 
 
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Effects of green tea on lipid metabolism in overweight or obese people: A 
meta-analysis of randomized controlled trials 
Yuan Fen1, Dong Hui2, Fang Ke3, Gong Jing4, Lu fuer5 
Institute of Integrated Traditional Chinese and Wertern Medicine, Tongji Hospital, 
Tongji Medical College,HuaZhong University of Science and Technology, Wuhan, 
Hubei430030, China 
Correspondence: Lu fuer (felu@tjh.tjmu.edu.cn ) 
Keywords: green tea/ lipid metabolism/ meta-analysis/ overweight/ obese 
Abbreviations: TG, triglyceride; TC, total cholesterol; EGCG, epigallocatechin 
gallate 
Scope: The effects of green tea on lipid metabolism were inconsistent. The 
objective of this meta-analysis was to evaluate the effects of green tea on lipid 
metabolism in overweight or obese people. 
Methods and results: We searched randomized controlled trials(RCTs) comparing 
green tea with a control on lipid metabolism on PUBMED and WEB OF SCIENCE 
(January 1990 to September 2016), COCHRANE and EMBASE (updated to 
https://doi.org/10.1002/mnfr.201601122
https://doi.org/10.1002/mnfr.201601122
https://doi.org/10.1002/mnfr.201601122
mailto:felu@tjh.tjmu.edu.cn%20(F
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October 2016), and the Chinese databases CNKI, WanFang and CBMD. Twenty-
one articles studying 1704 overweight or obese subjects were selected for this 
meta-analysis. The pooled results demonstrated that green tea significantly 
decreased plasma total cholesterol (TC) and low-density lipoprotein cholesterol 
(LDL) levels in overweight or obese people. The weighted mean difference was -
3.38mg/dl for TC (95% CI: -6.42, -0.33mg/dl) and -5.29mg/dl for LDL (95% CI: -
7.92, -2.66mg/dl), respectively. Green tea intake, however, showed no effect on 
plasma triglyceride (TG) and high-density lipoprotein cholesterol(HDL) levels in 
overweight or obese people with a relatively high heterogeneity. 
Conclusions: The meta-analysis shows that drinking green tea can lower plasma 
TC and LDL levels significantly. Nevertheless, green tea’s effect on plasma TG and 
HDL must be further evaluated by additional high-quality and large-scale RCTs. 
 
 
 
 
 
 
 
 
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GA-TEXT The flowchart shows the results of serching on the databses and the 
conclusions of this meta-analysis. 
 
1 Introduction 
Obesity or overweight is a global health problem that results from the interaction of 
eating habits with genetic and environmental factors that lead to energy 
imbalance[1]. Based on WHO statistics, the prevalence of overweight or obesity has 
increased twofold since 1980 and 52% of people aged 18 years and over were either 
overweight or obese in 2014[2]. In the USA, beyond two-thirds (68.8%) adults are 
diagnosed as either overweight (33.1%) or obese (35.7%)[3]. Spending on obesity is 
enormous in America and has become a large financial burden for society[4]. In 
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Europe, over 50% of the population is overweight or obese. The situation is 
exacerbated by the fact that the incidence of overweight or obesity in children and 
adolescents is surging[5]. Moreover, many countries consider obesity to be a 
disease and take action on treatment rather than prevention[6]. In America and 
Europe, overweight and obesity are defined as BMI >25 kg/m 2 or 30 kg/m2. In Asia, 
those whose BMIs are over 23kg/m2 or 25kg/m2 will be diagnosed as overweight or 
obese[7]. 
A series of studies about the relationship between obesity or overweight and 
dyslipidemia have been performed. Based on recent reports, obesity is harmful to 
lipid metabolism and causes dyslipidemia[8-11]. Dyslipidemia, which is the primary 
risk for cardiovascular diseases, is defined as an increase of plasma triglyceride 
(TG) or low-density lipoprotein cholesterol (LDL) or a decrease of plasma high-
density lipoprotein cholesterol (HDL)[12]. Increasing plasma LDL levels in the blood 
contribute to the development of atherosclerosis[13], and plasma HDL, which has a 
positive effect on myocardial infarction, is clearly reduced in dyslipidemia and loses 
its protective function against vascular disease[14]. Additionally, the increasing ratio 
of total cholesterol to HDL is the optimal marker of cardiovascular disease[15]. To 
decrease the risk of cardiovascular disease, medications including niacin and 
omega-3 fatty acid and statins are frequently used to alleviate dyslipidemia; 
however, their adverse effects, which include headaches, flushing, liver injury and 
abnormally high LDL, attract negative public attention[16-19]. A more effective and 
safe substance should be studied and applied to prevent and treat dyslipidemia. 
Tea, from Camellia Sinenis, is a popular beverage around the world, especially in 
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Asia, North Africa, the USA and Europe [20]. Tea can be classified as green tea, 
oolong tea or black tea depending on the manufacturing process. As a consequence, 
the ingredients across these types differ. Specifically, green tea is abundant with 
kaempferol glycosides, while oolong tea contains more quercetin and myricetin 
glycosides and black tea is rich in quercetin glycosides[21]. The benefical effects of 
tea on human health and fitness, however, is attributed to green tea, specifically its 
main component, catechin[22]. Catechin is a vital compound that contains 
epigallocatechin gallate (EGCG), epicatechin gallate (ECG), epigallocatechin (EGC), 
and epicatechin (EC)[23]. Of these, EGCG is the major and functional 
component[24]. Generally, the proportion of catechin is 30–42% of the dry green tea 
leaves (e.g., 2.5 g of tea leaves in 250 mL hot water holds 240–320 mg of catechin), 
and 60–65% of catechin is EGCG[25]. 
According to recent studies, green tea could function to mitigate inflammation, 
hypertension and some cancers[26-28]. Moreover, many studies have shown that 
green tea has a positive effect on the metabolism of lipid by different mechanisms. 
Huang proved that green tea could reduce food intake and lipid absorption[29]. 
Wang and Sae-tan concluded that green tea catechins restrained the proliferation of 
adipocytes and the accumulation of TG[30, 31]. Suzuki-Sugihara demonstrated that 
green tea catechins could decrease LDL oxidation to reduce cardiovascular risk[32]. 
Controversies remain, however, regarding the effects of green tea on plasma lipid 
metabolism as demonstrated in clinical trials, especially for overweight or obesity. 
Some clinical experiments show that green tea consumption has no effect on any 
lipid profiles[33-41], while other clinical studies show that its effects on lipid 
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metabolism are significant[42-52]. Moreover, there has been no meta-analysis of the 
effect of green tea on lipid metabolism in the overweight or obese. 
Thus, we perform this meta-analysis to evaluate the effects of greentea on lipid 
metabolism in people with overweight or obesity based on published randomized 
controlled trials that only recruited subjects who are overweight or obesity. This 
analysis may help us to find an effective alternative to regulate the lipid metabolism. 
2 Subjects and methods 
2.1 Search and selection 
 PUBMED and WEB OF SCIENCE (January 1990 to September 2016), in addition to 
COCHRANE, EMBASE, the Chinese databases CNKI and WanFang and CBMD 
(updated to October 2016) were utilized to search randomized controlled trials 
(RCTs) on the effects of green tea on lipid metabolism. The key words consisted of 
green tea, Camellia Sinensis, green tea extract, tea polyphenol*, catechin, 
epigallocatechin gallate, EGCG, epicatechin gallate, ECG, epigallocatechin, EGC, 
epicatechin, EC, lipid*, triglyceride, TG, total cholesterol, TC, low density lipoprotein 
cholesterol, LDL-C, high density lipoprotein cholesterol, HDL-C, lipid metabolism, 
glucose, diabetes mellitus, insulin, glycemic, metabolic syndrome, MS, glycaemic, 
and non insulin dependent diabetes mellitus. The search was limited to clinical trials 
with human subjects. 
Studies were selected for this meta-analysis if they met the following criteria: (i) 
The duration of intervention was over 2 weeks; (ii) Green tea or green tea exact was 
the only supplement used, rather than mixing green tea with other subjects such as 
oolong tea, black tea or grape seeds; (iii) The participants were overweight 
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(BMI>25kg/m2 in America and Europe or 23kg/m2 in Asia) or obese (BMI >30kg/m2 in 
America and Europe or 25kg/m2 in Asia); (iv) Parallel or crossover RCTs in human 
beings were conducted; (v) All data were available including the baseline and 
endpoint values or net changes between them with mean, standard deviation, and 
number of participants available, or 95% confidence intervals for the experimental 
and control groups; (vi) All studies had to contain at least one of following statistics: 
plasma TG, TC, LDL or HDL levels; and (vii) The trials had to show the comparison 
between the treatment and control groups. 
 2.2 Quality assessment 
The Jadad scale was used to assess the quality of selected studies[53]. The items 
were shown as follows: (1) process of randomness (0-2 points); (2) double-blinding 
(0-2 points); (3) concealment of allocation (0-2 points); and (4) reporting dropouts 
and withdrawals (0-1 points). The score of the high-quality study was four or more. 
2.3 Data collection 
The following data were collected from the studies (see Table 1 and Supporting 
Information Table 1): 1) Study characteristics, including authors, publication year, 
study design, dose, and periods of intervention, formulation of green tea, Jadad 
score, decaffeination of green tea, percentage of caffeine and EGCG dose; 2) 
Participants’ information including countries of origin, average ages, BMI, physical 
condition, and type of lifestyle; 3) Study outcomes, including plasma TG, TC, LDL, 
and HDL. All lipid values were transferred into mg/dl, and the index of the conversion 
formula was as follows: 1) 1mmol/l TG=88.6mg/dl TG; 2) 1mmol/l TC or LDL or HDL 
=38.7mg/dl TC or LDL or HDL. If trial included different doses of green tea treatment 
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groups, we divided them into two trials with the same control group[53]. If trial 
contained several different treatment groups that were compared with a control 
group, we only extracted the information on the green tea or green tea extract and 
control groups. If trial was designed with crossovers, we only extracted the first stage 
data before the subjects were told to exchange interventions[54]. For inaccurate 
data, we contacted study authors via emails to request their original data. We 
excluded those studies whose authors refused to provide original data. 
2.4 Statistics and analysis 
STATA software (version 14; StataCorp) was applied for our meta-analysis. The 
outcomes of net change between the treatment groups and control groups were 
shown with weighted mean differences (WMD) and 95% CI for TG, TC, LDL, and 
HDL. The heterogeneity between studies was assessed using Cochrane’s test 
(p<0.1). The I2 was checked; we considered I2>50% to indicate high heterogeneity 
between studies and the corresponding p-value >0.1 was considered low 
heterogeneity[55]. The outcomes were generated from a fixed-effects model if the 
I2<50%, otherwise, a random-effects model was used to analyse data. Z-scores were 
used to evaluate overall effects. The overall effect was reckoned with statistic 
meaning when the linked p value was less than 0.05. Publication bias and sensitivity 
analysis were assessed using Egger’s regression test. 
2.5 Subgroup analysis 
The purpose of subgroup analysis was to discover the source of heterogeneity. 
Thus, we conducted seven subgroups to analyse the heterogeneity, including the 
duration of intervention (≥12weeks or <12weeks); dose of EGCG (EGCG≥400 or 
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<400mg); continent (America, Europe or Asia); decaffeination of green tea or not; 
the Jadad score (≥4 or <4); subjects with or without a hypocaloric diet; and 
participants with or without complications. The exercise subgroup was not conducted 
because of small sample size of trials available for this meta-analysis. 
3 Results 
A total of 1058 English articles and 394 Chinese articles were searched. Nine 
hundred and seventy-eight articles were excluded(272 duplicated articles; 20 no 
placebo articles; 81 cell; 109 other animals; 650 no relation; 47 green tea or green 
tea extract mixing with others; 66 only other tea; 129 reviews) after reading titles and 
abstracts. An initial, 78 articles were selected. After further sifting, 21 articles were 
selected to complete the meta-analysis: 15 articles including 18 trials for TG[33, 35, 
37, 40-47, 50, 52, 56, 57] , 18 articles including 21 trials for TC[33-37, 39-47, 51, 52, 
56, 57], 19 articles including 21 trials for LDL[33-37, 39-49, 51, 52, 57], and 20 
articles including 22 trials for HDL[33-37, 39-52, 57]. The process is presented in 
Figure 1. 
3.1 Study characteristics 
In total, 21 articles including 24 trials enrolling 1704 subjects were included, with 866 
participants in the treatment group and 838 subjects in the control group. The study 
attributions are shown in Table 1. All of the subjects were overweight or obese. In 
details, trials tested following: six trials enrolled people with early metabolic 
syndrome, borderline metabolic syndrome or defined metabolic syndrome; three 
trials enrolled people with type 2 diabetes; two trials enrolled people with 
hypertension; and another thirteen trials enrolled people with only overweight or 
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obesity. Seven trials were conducted in Asia; eleven trials were performed in Europe, 
and the remainder occurred in America. The ages of participants varied from 6 to 
over 80 years. The periods of treatment ranged from six weeks to twenty-four weeks. 
The dosage of EGCG reported was from 39 mg to 856.8 mg per day, and six 
trials did not describe the specific dosage of EGCG. All of the trials were RCTs. 
Twenty-two were parallel trials, of which thirteen were double blind, five were single 
blind, and four were non-blind. Two were crossover trials, one of which was double-
blind and the other was non-blind. One trial conducted by Maki[52] required people 
to exercise, and fourtrials restrained to energy intake[34, 35, 49, 51]. One trial asked 
participants to refrain from dieting but to exercise[50]. Other trials were keeping 
usual lifestyle but limited to ingest extra green tea, green tea supplements or 
catechin-rich food. Nine trials were of high quality (Jadad score ≥ 4)[33, 34, 36, 39, 
42, 44, 46-48]. The percentage of caffeine, which was similar in most paired 
treatment and control groups, varied from 0 to 79.4% and 77.7% in treatment and 
control groups respectively. However, four trials did not reported the exact 
percentage of caffeine in both groups[37, 51, 56]. 
Publication bias was estimated by Egger’s test. Studies with p values over 0.05 
were considered to exhibit low bias. The outcomes demonstrated that there were 
insignificant publication bias of TG, TC, LDL and HDL(TG Egger’s test: P=0.202; TC 
Egger’s test: P=0.617; LDL Egger’s test: P=0.812; HDL Egger’s test: P=0.647). 
(Supporting Information Figure 1). 
 
 
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3.2 Effect of green tea on plasma TG levels among people with overweight or 
obesity 
Eighteen trials with 584 subjects in the treatment group and 553 in control group 
reported baseline data and endpoint values regarding plasma TG levels. Under a 
fixed-effects model, the average change in TG values between the treatment and 
control groups was -7.02mg/dl (95% CI:-14.58, 0.54mg/dl). The heterogeneity I2 
(variation in WMD attributable to heterogeneity) was 28.5% and the related p-value 
was 0.126. The Z score was 1.82 and the corresponding p-value was 0.069. This 
suggested green tea had no significant effect on plasma TG levels in people with 
overweight or obesity (Figure 2). 
3.3 Effect of green tea on plasma TC levels among people with overweight or 
obesity 
Twenty-one trials analysed the effect of green tea on plasma TC levels. 744 
overweight or obese people were in the experimental group and 710 participants 
were in the control group. Under a fixed-effects model, the net change between two 
groups was significant, as the data show: -3.38mg/dl (95% CI: -6.42, -0.33mg/dl) 
(Figure 3). The heterogeneity I2 (variation in WMD attributable to heterogeneity) was 
0.0% and the related p-value was 0.549. The Z score was 2.17 and the 
corresponding p-value was 0.03. According to these results, green tea showed 
beneficial effects on decreasing plasma TC levels in people with overweight or 
obesity. 
 
 
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3.4 Effect of green tea on plasma LDL levels among people with overweight or 
obesity 
Twenty-one trials were selected to perform the analysis. There were 726 and 712 
subjects in the intervention and control groups, respectively. We used a fixed-effects 
model to analyze the data. As a consequence, there was a remarkable decrease in 
plasma LDL levels. The difference between the two groups was -5.29mg/dl (95% CI: 
-7.92, -2.66mg/dl) (Figure 4). The heterogeneity I2 (variation in WMD attributable to 
heterogeneity) was 1% and the related p-value was 0.588. The Z score was 3.94 
and the corresponding p-value was 0.000. 
3.5 Effect of green tea on plasma HDL levels among people with overweight or 
obesity 
Twenty-two trials containing 1534 subjects (772 of them in the treatment group, the 
remainder in the control group) were used to analyse the effect of green tea on 
plasma HDL levels. With a random-effects model, the net change between the 
treatment and control groups was 1.13mg/dl (95% CI: -0.24, 2.51mg/dl) (Figure 5). 
The heterogeneity I2 (variation in WMD attributable to heterogeneity) was relatively 
high at 51.4%, and the related p-value was 0.002. The Z score was 1.62 and the 
corresponding p-value was 0.105. 
3.6 Analysis of subgroup and sensitivity 
The outcomes of TG, TC, LDL, HDL are shown in the Supporting Information Tables 
2, 3, 4 and 5, respectively. According to the attributions of participants, we 
conducted seven subgroups to analyse the source of heterogeneity, which included 
the dosage of EGCG, duration of intervention, continents, complications, diets, the 
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quality of study and decaffeination. 
In the dosage subgroup, there was no heterogeneity for all lipid values in the high 
subgroup (EGCG≥400mg/d). However, green tea only showed significant effects on 
plasma LDL levels in this subgroup. We also analysed the subgroup of the duration 
of each intervention. An obvious benefit occurred in the long-term subgroup 
(≥12weeks) for plasma TC, LDL and HDL levels, but not for plasma TG levels. In the 
complication subgroup, green tea showed powerful effects on plasma LDL level in 
subjects with or without complications. In addition, we found a benefit of green tea 
for TG with low heterogeneity in trials that enrolled subjects with other complications. 
Nevertheless, a large decrease in plasma TC levels was found in the subgroup of 
the subjects without complications. In the subgroup stratified by continents, green 
tea had significant benefits on TG in the Europe subgroup and on LDL in both the 
Asia and Europe subgroups. In the subgroup divided by decaffeination, green tea 
consumption showed an obvious benefit for plasma TG levels in the decaffeination 
subgroup; however, it had a powerful effect on plasma LDL levels not only in the 
decaffeinated subgroup but also in the undecaffeinated subgroup. In the subgroup of 
hypocaloric diet, the green tea supplement showed a lowering effect on plasma HDL 
levels. A powerful effect of green tea on plasma TC and LDL levels was also shown 
in isocaloric diet subgroup. In Jadad score subgroup, green tea was only good for 
lowering plasma TG levels in the high quality subgroup (Jadad score ≥4) and for 
plasma LDL levels in both high(Jadad score ≥4) and low (Jadad score <4)quality 
subgroups. The results of the sensitivity analysis of lipid parameters were detected 
with STATA software. The pooled effects of trials were analogous (Supporting 
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Information Figure 2). 
4 Discussion 
This meta-analysis is the first to study the effects of green tea on lipid parameters in 
overweight or obese people. Although some meta-analysis have shown that green 
tea had significant effects on TC and LDL but no effect on TG and HDL[58-60], not 
all of them examine the effects of green tea on lipid metabolism in overweight or 
obese people. Whether green tea has a more profound influence on lipids 
metabolism in overweight or obese people is unclear. According to the outcomes, 
green tea could significantly decrease plasma TC and LDL levels, but, it is not good 
for TG and HDL. Those results may suggest that green tea carries no additional 
benefits for overweight or obese subjects. Although the results for plasma HDL 
showed a duration-dependent effect of green tea according to the analysis of the 
duration subgroup, the heterogeneity is significant (63%). Thus, the results did not 
demonstrate that long-term green tea intake could better modulate the lipid 
metabolism in overweight or obese people. 
Previous studies reported that EGCG was the major hypolipidemic component in 
green tea, and its mechanisms may be associated with decreasing the absorption of 
lipids and attenuating inflammation[61-63]. Therefore, we performed the subgroup 
analysis of the dosage of EGCG to detect whether green tea had more significant 
effects on levels of plasma lipids with a high dosage of EGCG. To our surprise, 
green tea only showeda benefit for decreasing the plasma LDL levels in both 
high(≥400mg/d) and low (＜400mg/d) dosage of EGCG subgroups, but not for other 
lipid parameters(TG, TC, HDL) in the blood. Even, the high dose EGCG did not 
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significantly alleviate TC levels, which conflicted with the meta-analysis[64]. This 
may suggest that 400mg/d was not reasonable critical value to define a high or low 
subgroup for overweight or obese people. Moreover, several trials did not report the 
exact dose of EGCG. Therefore, the dose-different impact of EGCG must be studied 
further. 
There is a close relationship between diet and lipid metabolism; therefore, we 
conducted a subroup analysis of calories. Green tea consumption showed no benefit 
for plasma TG levels in the hypocaloric diet subgroup. This may conflict with the 
article that demonstrated dietary interventions had beneficial effects on plasma TG 
levels[65]. It could not be denied, however, that a hypocaloric diet was not good for 
blood lipid profiles because only two trials were included in hypoclaric subgroup. 
What was surprising was that the green tea showed significant effects on plasma TC 
and LDL levels in the isocaloric diet subgroup with no hetergeneity, rather than in the 
hypocaloric diet subgroup. Although the outcomes were inconsistent with the 
conclusion of Sonego, who demonstrated that a healthy diet was good for lipid 
metabolism[66], we could infer that the green tea definitely had good effects on 
plasma TC and LDL levels. The main reason that the green tea had no effects on 
plasma TC and LDL levels might be the small number of subjects included in the 
hypocaloric diet subgroup. Hence, more studies enrolling subjects with a hypocaloric 
diet are needed to research the relationship between diet and lipid metabolism. 
Caffeine, one of the bioactive components of green tea, has been demonstrated to 
reduce plasma cholesterol and TG levels[67]. Thereby, a subgroup stratified by 
decaffeination was performed to analyse whether green tea components of caffeine 
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and green tea catechins exerted synergistic effect on lipid metabolism in overweight 
or obese people. Surprisingly, green tea had a significant effect on plasma LDL 
levels in the both decaffeinated and undecaffeinated subgroups. In contrast with the 
undecaffeinated subgroup, however, green tea showed an obvious benefit to plasma 
TG levels in the decaffeinated subgroup. The result partly conflicted with the animal 
experiment performed by Zhao, which showed that the combination of caffeine and 
catechins improves the metabolism of lipids through activating the corresponding 
enzymatic bio-activities[68]. The reason for this outcome may be that most 
participants in the selected trials did not limit their intake of caffeine from other foods 
or beverages so that the effect of green tea on TG in the decaffeinated subgroup 
was reversed. 
In addition, the subjects we included varied from healthy overweight or obese 
individuals to unhealthy overweight or obese individuals experiencing complication 
from diabetes, metabolism syndrome or hypertension. We conducted a 
complications subgroup analysis to detect the heterogeneity. An interesting 
phenomenon was found in TG group. In the subgroup with complication, the green 
tea showed a statistically significant difference on TG but had no such effect in the 
subgroup without complications. This may suggest that the effect of green tea on TG 
is more pronounced in overweight or obese individuals who may be with higher 
plasma TG. 
There are several limitations in our meta-analysis. First, more than half of trials 
were low-quality (Jadad score <4). Therefore, it may cause false positive or false 
negative results in this subgroup because of subjectivity. For instance, although 
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green tea did not show good results for plasma TG levels overall, it had an obvious 
shrinking effect on plasma TG levels in the high quality subgroup. More high quality 
studies are necessary to analyse the effects of green tea on lipid metabolism in 
overweight or obese people. Second, the ages of subjects ranged from children to 
the elderly, and the green tea supplement offered to the subjects varied from pure 
EGCG to green tea without purity. Other components included in green tea also 
have a positive effect on lipid parameters[69]. All of these factors may contribute to 
the heterogeneity. Third, some studies did not report the exact dosage of EGCG that 
might cause the paradoxical effect in the dosage subgroup analysis. Additionally, 
some articles were excluded for the unavailable data[70, 71], and the search was 
limited to the English and Chinese databases that may confound the outcomes. 
Finally, although the adverse affairs of green tea had been reported in some trials 
[33, 34, 44, 46], most of the subjects in the trials would heal without treatment in the 
first week of intervention, and few people stopped participating for this reason. This 
finding demonstrated that the safety of green tea was great even for long-term or 
heavy dosage. 
In conclusion, our meta-analysis suggested that green tea was good for 
decreasing plasma TC and LDL levels in overweight or obese people, especially for 
long-term consumption. The effects of green tea on decreasing plasma TG and 
increasing HDL levels were not supported, however, although green tea showed a 
positive effect on them in some subgroups. More high-quality and long-term trials are 
needed for further characterisation of the effects of green tea on serum lipids in 
overweight or obese people. 
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Y.F designed the study and wrote this article; F.K. an G.J searched reference and 
extracted data; D.H. and L.F gave pertinent advices and careful revision. 
 
This article is supported by the National Natural Science Foundation of China (No. 
81473637, 81373871, 81673928). 
 
There is no conflict of interests among the authors. 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
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Table 1 The characteristics of studies and participants included in this meta-
analysis. 
Study Country Study design 
Hsu et al.(2011) China RP; DB 
Nagao et al.(2007) Japan RP; BD 
Chen et al.(2016) China RP; DB 
Matsuyama et al.(2008) Japan RP; DB 
Mielgo-Ayuso et al. (2014) Spain RP; DB 
Diepvens et al.(2006) Netherlands RP; DB 
Hsu et al.(2008) China RP; DB 
Stendell-Hollis et al.(2010) USA RP; DB 
Bogdanski et al.（2012） Poland RP; DB 
Suliburska et al.(2012) Poland RP; DB 
Brown et al. (2009) UK RP; DB 
Senger et al.(2012) Brazil RP 
Mousavi et al.(2013)a Germany RP 
Mousavi et al.(2013)b Germany RP 
Brown et al.(2011) UK RC; DB 
Pierro et al.(2009) Italy RC 
 Belcaro et al.(2013) Italy RP; SB 
Basu et al.(2011)a USA RP; SB 
Basu et al.(2011)b USA RP; SB 
 Sanchez et al.(2005)a USA RP; SB 
Sanchez et al.(2005)b USA RP; SB 
 Maki et al.(2009) USA RP; DB 
Tsai et al.(2009) China RP 
Tsuchida et al.(2002) Japan RD; DB 
 
 
 
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Table 1 continued 
Number of 
subjects 
(treatment/control) 
Age of participants(year) 
,mean±SD,(treatment/co
ntrol) 
BMI(treatment/control) 
kg/m2 
35/33 50.5 ±9.2/52.2±9.1 30.3±4.3/29.2±3.6 
123/117 41.7 ± 9.9 26.9±1.9/26.7±2.1 
39/38 44.1±10.9/44.9±11.9 31.0±3.8/30.0±3.5 
19/19 6–16 27.2±3.67/27.4± 3.92 
43/40 33.7±2.6 /34.3±3.0 30-40 
23/23 41.7±8.6/41.6±10.0 27.7±1.8/27.7±1.8 
41/37 43.0 ±11.1/43.9±12.631.2±3.5/30.5±4.6 
23/16 56.6±8.1/57.8±8.5 31.0±4.3/28.7±3.8 
28/28 49.2±8.8/51.5±7.4 32.5 ± 3.3/33.9 ± 2.3 
23/23 48.56±8.81/52.26±7.71 32.07±2.41/33.45±2.65 
46/42 52.15 ±6·43/50.57±6.48 31.21±2.80/30.96±2.45 
24/21 ≥60 30.5±4.3/30.4±4.5 
24/14 54.6±9.6/52.0±8.2 27.4±2.8/28.1±3.0 
25/14 56.2±8.5/52.0±8.2 28.1±3.3/28.1±3.0 
67/70 49.5±5.6/49.4±5.6 31.7±2.7/31.4±2.6 
50/50 25-60 28-36 
48/50 47.6 ±5.5/45.3±3.55 31.0±2.0/30.9±2.6 
 13/12 42.8±9.4/44.6±11.1 36.1±1.3 
 10/12 39.5±9.5/44.6±11.1 36.1±1.3 
 7/11 >21 38.6±1.5/37.4±2.8 
 5/11 >21 41.5±2.1/37.4±2.8 
51/56 21-65 32.2±0.5/32.2±0.5 
60/60 25-65 35-38 
39/41 30-65 24-30 
 
 
 
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Table 1 continued 
Dosage of 
EGCG(mg/d) 
Duration of 
intervention 
Green tea 
decaffeinated 
Percentage of caffeine 
(%)(treatment/control) 
856.80 16 weeks yes None 
103.00 12 weeks no 72.3/ 75.0 
856.80 12 weeks yes None 
102.50 24 weeks no 79.4/ 77.7 
300.00 12 weeks yes None 
595.80 87 days no 16.4/ 0 
377.15 12 weeks no 0.69/ 0 
128.80 6 months yes None 
208.00 3 months yes None 
208.00 3 months yes None 
800.00 8 weeks yes None 
Unclear 60 days no Unreported 
Unclear 8 weeks no Unreported 
Unclear 8 weeks no Unreported 
430.00 6 weeks yes None 
Unclear 90 days yes None 
Unclear 24 weeks yes None 
440.00 8 weeks yes None 
500.00 8 weeks yes None 
400.00 8 weeks yes None 
500.00 8 weeks yes None 
214.00 12 weeks no 7.8/ 7.8 
Unclear 12 weeks no Unreported 
115.00 12 weeks no 24.4/ 23.9 
 
 
 
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Table 1 continued 
Physical condition 
Jadad 
score 
Daily dosage of treatment/control 
Obesity with T2DM 7 1500mg decaf-GTE/ cellulose 
 Visceral fat-type obese 3 9g GT/ control 
 Central obesity 7 1500mg decaf-GTE/ cellulose 
Obese/near-obese 3 576 mg catechins/ 75mg catechins 
 Pre-menopausal obese 7 300mg EGCG/ lactose. 
 Overweight 3 1443.6mg GT/ placebo 
Obese 7 1200mgGTE/ placebo 
 Overweight/obese 5 960ml decaf-GT/ placebo 
 Obese with hypertensive 4 379mg GTE/ placebo 
 Obese with hypertension 5 379mg GTE/ placebo 
Overweight/ obese male 5 800mg EGCG/ placebo 
 Metabolic syndrome 3 3g GT/ placebo 
Overweight/ obese with T2DM 2 4cups GT/ control 
Overweight/ obese with T2DM 2 2cups GT/ control 
Overweight and obese 7 800mg decaf-catechins/ placebo 
Obese 1 300mg GTE/ placebo 
Borderline for MS 2 300mg GT catechin/ placebo 
Obese with MS 2 4cups GT/ water 
Obese with MS 2 2capsules GTE/ water 
MS 2 4cups GT Beverage/ water 
MS 2 2capsules GTE/ water 
 Overweight and obese 2 625mg catechins /control beberage 
Obese 1 6g GT/ control 
Overweight or obese 2 588mg catechin/126mg catechin 
 
 
 
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Table 1 continued 
Formulation Lifestyle 
 Capsure Usual lifestyle 
 Beverage Usual lifestyle 
 Capsure Usual lifestyle 
 
Beverage Usual lifestyle 
 Capsule Hypocaloric diet 
 Capsule Hypocaloric diet 
 Capsule Usual lifestyle 
 Beverage Usual lifestyle 
 Capsule Usual lifestyle 
 Capsule Usual lifestyle 
 Capsule Usual lifestyle 
 Beverage Usual lifestyle 
 Beverage Usual lifestyle 
 Beverage Usual lifestyle 
 Capsule Usual lifestyle 
 Tablet Hypocaloric diet 
 Tablet Exercise and hypocaloric diet 
 Beverage Usual lifestyle 
 Capsule Usual lifestyle 
 Beverage Usual lifestyle 
 Capsule Usual lifestyle 
 Beverage Exercise 
 Powder Hypocaloric diet 
 Beverage Usual lifestyle 
 RP, random parrallel trial; RC, random crossover trail; DB, double-blinding; SB, 
single-blinding; GTE, green tea extract; decaf-GTE, decaffeinated green tea extract 
EGCG, epigallocatechin gallate; GT, green tea, decaf-GT, decaffeinated green tea ; 
decaf-catechins, decaffeinated catechins; T2DM, type 2 diabetes mellitus; MS, 
metabolic syndrome 
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33 
 
 
Figure 1. Flowchart showing the process of selecting, including, and excluding 
articles by individuals for this meta-analysis. 
 
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Figure 2. Effect of green tea compared with control on plasma triglyceride levels. 
Weight was analysed with STATA software by using the number of participants, 
mean and SD in treatment and control groups. The diamond indicates the pooled 
effect, and the outcome was obtained from a fixed-effects model. WMD, weighted 
mean differences. 
 
 
 
 
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35 
 
 
Figure 3. Effect of green tea compared with control on plasma total cholesterol 
levels. Weight was analysed with STATA software by using the number of 
participants, mean and SD in treatment and control groups. The diamond indicates 
the pooled effect, and the outcome was obtained from a fixed-effects model. WMD, 
weighted mean differences. 
 
 
 
 
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Figure 4. Effect of green tea compared with control on plasma low-density 
lipoprotein cholesterol levels. Weight was analysed with STATA software by using 
the number of participants, mean and SD in treatment and control groups. The 
diamond indicates the pooled effect, and the outcome was obtained from a fixed-
effects model. WMD, weighted mean differences. 
 
 
 
 
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Figure 5. Effect of green tea compared with control on plasma high-density 
lipoprotein cholesterol levels. Weight was analysed with STATA software by using 
the number of participants, mean and SD in treatment and control groups. The 
diamond indicates the pooled effect, and the outcome was obtained from a random-
effects model. WMD, weighted mean differences.