Effect of green tea extract on obese women: A
randomized, double-blind, placebo-controlled
Chung-Hua Hsua,b,c, Tung-Hu Tsaid, Yung-Hsi Kaoe, Kung-Chang Hwangf,
Ting-Yu Tsengd, Pesus Choua,b,*
aCommunity Medicine Research Center, National Yang-Ming University, Taipei, Taiwan
bInstitute of Public Health and Department of Public Health, School of Medicine,
National Yang-Ming University, Taipei, Taiwan
cDepartment of Chinese Medicine, Taipei Hospital, Taipei County, Taiwan
dInstitute of Traditional Medicine, National Yang-Ming University, Taipei, Taiwan
eDepartment of Life Science, College of Science, National Central University, Taoyuan County, Taiwan
fDepartment of Pediatrics, Taipei Hospital, Taipei County, Taiwan
Received 25 September 2007; accepted 18 March 2008
Green tea extract;
Aims: To examine the effect of green tea extract (GTE) on obese women and to explore the
relationship between GTE and obesity-related hormone peptides.
Methods: A randomized, double-blind, placebo-controlled clinical trial was conducted from
July 2006 to June 2007 in Taipei Hospital, Taiwan. Seventy-eight of 100 obese women aged be-
tween 16 and 60 years with BMI > 27 kg/m2and who had not received any other weight control
maneuvers within the last 3 months completed this study. The subjects were randomly divided
into Groups A and B. Group A (n Z 41) received GTE while Group B (n Z 37) took cellulose as
a placebo, one capsule (400 mg) three times each day for 12 weeks. The body weight (BW), body
mass index (BMI) and waist circumflex (WC) were measured at the beginning of the study and
after 12 weeks of treatment with GTE. The data were compared and expressed as % reduction.
Results: There was only a 0.3% reduction in BW (0.15 kg) after 12 weeks of treatment with GTE.
There was no statistical difference in % reduction in BW, BMI and WC between the GTE and pla-
cebo groups. Within group comparison revealed that the GTE group had significant reduction in
LDL-cholesterol and triglyceride, and marked increase in the level of HDL-cholesterol, adipo-
nectin and ghrelin. On the other hand, the placebo group showed significant reduction in
* Corresponding author. Community Medicine Research Center and Institute of Public Health, National Yang-Ming University, Taipei,
Taiwan, 155, Li-Nong St, Sec 2, Peitou, Taipei, Taiwan. Tel.: þ886 2 2826 7050; fax: þ886 2 28201461.
E-mail address: email@example.com (P. Chou).
0261-5614/$ - see front matter ª 2008 Elsevier Ltd and European Society for Clinical Nutrition and Metabolism. All rights reserved.
available at www.sciencedirect.com
Clinical Nutrition (2008) 27, 363e370
triglyceride only, and a marked increase in the level of ghrelin alone.
Conclusions: This study showed no statistical difference in % reduction in BW, BMI and WC be-
tween the GTE and placebo groups after 12 weeks of treatment. The intake of GTE (491 mg cat-
echins containing 302 mg EGCG) for 12 weeks is considered safe as shown by the results.
ª 2008 Elsevier Ltd and European Society for Clinical Nutrition and Metabolism. All rights
Obesity is becoming a global epidemic and common health
problem. More than 50% of Americans have BMI > 27 kg/
m2.1e4It has been reported that the prevalence of obesity
in the United States increased 50% from 1991 to 1998.5
The same trend was noted in Taiwan.6e7Furthermore, the
incidence and prevalence of obesity are increasing world-
wide, especially in the developing and newly industrialized
nations. Obesity is related to diabetes mellitus, hyperlipid-
emia and cardiovascular diseases, which are major diseases
in Taiwan and other developing countries.8e9
Green tea is one of the most popular beverages in the
world. It is believed to have beneficial effects in prevention
and treatment of many diseases, one of which is obesity.10e
13An epidemiological human study showed that consump-
tion of tea for more than 10 years led to a lower percentage
of total body fat and smaller waist circumfluence.14The
anti-obesity effects of green tea are mainly attributed to
its polyphenol content, in particular, epigallocatechin gal-
late (EGCG),15which is most abundant in green tea and
has been found to inhibit adipocyte proliferation and differ-
entiation in in vitro studies.16e18
Many human studies have been designed to examine the
effects of green tea extract (GTE) with high EGCG content
on weight and fat control, and most of these studies have
found a significant decrease in body weight and body fat
when compared with the baseline measurements.18e24How-
ever, many of these reports lacked a controlled design,18e19
were of short duration,20,21had small sample sizes,20e23
were combined with other weight control methods22e24or
had not explored obesity-related hormone peptides.18e24
We hypothesized that GTE would help reduce body weight
by influencing obesity-related hormone peptides. Thus, we
conducted this randomized clinical trial to examine the
effect of GTE on obese women and to explore the relation-
ship between GTE and obesity-related hormone peptides.
Study design and participants
The trial was conducted from July 2006 to June 2007 in
screened at our outpatient clinic, a total of 100 were
enrolled. The subjects had to be between 16 and 60 years
old and with BMI > 27 kg/m2. The exclusion criteria were:
(1) endocrine disease, e.g. thyroid disorder, pituitary disor-
der, and sex gland disorder; (2) heart disease, e.g. arrhyth-
mia, heart failure, myocardial infarction, and patient with
pacemaker; (3) allergy and immunology disease; (4) high
aminotransferases (alanine, aspartate > 80 IU/L) or high
serum creatinine (>2.5 mg/dl); (5) pregnant or lactating
women; (6) childbirth within 6 months; (7) stroke or other-
wise unable to exercise; (8) management for weight control
within 3 months; and (9) any other conditions deemed un-
suitable for trial as evaluated by the physician-in-charge.
The enrolled patients were randomly allocated to receive
GTE (Group A) or a placebo (cellulose; Group B) for 12 weeks
(Fig. 1). The protocol was approved by the Human Ethics
Committee of our hospital. Informed consent was obtained
from all the enrolled patients. In the lead-in period of
2 weeks, the patients should maintain weight and WC within
0.5% and were given detailed explanation of the study de-
sign; they were then randomly assigned to one of the two
study groups. The subjects were not allowed to receive
otherobesity managementand wereasked tokeep theirfor-
mer diet during the study period. For 4 weeks, every subject
had to come once a week to the hospital for a blood sample
to be taken and for us to assess his/her compliance in con-
suming the amount of GTE prescribed. All subjects were
free to withdraw at any time during the course of the study.
Randomization and blindness
All subjects were randomly assigned to one of the two
above-mentioned groups. A random number between 0.0
and 0.99 was generated by the computer for each subject.
Subjects with a random number between 0.0 and 0.49 were
assigned to the group with GTE, while those with a random
number between 0.50 and 0.99 were assigned to the
placebo group with cellulose. The same opaque capsules
containing either dried powdered GTE or placebo (cellulose)
were administered to the subjects by a research assistant
blinded to the contents in the capsules. All subjects were
treated in the same fashion.
Preparation of sample and treatment
Our GTE samples, obtained from the Tea Research and
Extension Station, Taiwan, were extracted from dried
leaves of green tea according to the pre-set standard
procedures with certificate of analysis given. The placebo
given to the control group comprised pure microcrystalline
cellulose. The subjects were asked to take one capsule
containing 400 mg of either GTE or cellulose three times
each day for 12 weeks. The above capsule was taken
30 min after meals. Table 1 shows the components of caf-
feine and polyphenols in the capsules.
The outcome was evaluated as % reduction in BW, BMI and
WC after 12 weeks of intervention. All measurements were
364C.-H. Hsu et al.
done after an overnight fast using standardized methods
and were performed at the beginning of the study and after
12 weeks of treatment. The subjects were measured in
their undergarments with a hospital gown on. Height was
measured with a wall-mounted stadiometer to the nearest
0.1 cm, weight was measured on a calibrated balance beam
scale to the nearest 0.1 kg, and BMI was calculated
according to the formula: BMI Z body weight (BW)/height
(kg/m2). WC was measured mid-way between the lateral
lower rib margin and the iliac crest, and hip circumference
(HC) was measured at the levels of the major trochanters
through the pubic symphysis, with the scale to the nearest
0.1 cm. We simultaneously collected the demographic data
and fasting laboratory data such as blood sugar, creatinine,
aminotransferases aspartate, aminotransferases alanine,
uric acid, and plasma lipoproteins (triglyceride, choles-
terol, HDL-cholesterol (HDL) and LDL-cholesterol (LDL)).
Hormone peptides analysis
At baseline and after 12 weeks of treatment, insulin, adipo-
nectin, leptin and ghrelin of both groups were measured.
(HOMA-IR) [fasting glucose (mmol/l) ? fasting insulin (UI/
l)/22.5] was used as insulin resistance measurement.25e26
All measurements were made using standardized methods
at 0800e0900 h after an overnight fast. A sample of whole
blood was drawn and centrifuged at 4?C, and a 1-ml aliquot
of serum was rapidly frozen (?80?C) for subsequent hor-
mone analysis. The plasma adiponectin concentration was
measured by a radioimmunoassay kit (Linco Research,
for insulin resistance
336 registered obese women for screening
100 randomly assigned
2. (29 yrs, 31 yrs); Discontinued
3. (40 yrs, 44 yrs, 50 yrs); No effect
1. (42 yrs); Got sick
1. (50 yrs); Hospitalized
1. (55 yrs); Go Abroad
1. (43 yrs); Lost follow-up
3. (39 yrs, 27 yrs, 31 yrs); Discontinued
5. (40 yrs, 42 yrs, 43 yrs, 43 yrs, 51 yrs); No effect
1. (45 yrs); Got sick
4. (37 yrs; 23 yrs, 26 yrs, 24 yrs); Lost follow-up
154 met inclusion criteria and were invited to participate
36 refused to participate
2 excluded during lead-in period
Green Tea Extract
(n = 50)
(n = 50)
Weeks 12 (n = 41)
Weeks 12 (n = 37)
Trial profile and design.
Components of caffeine and polyphenols (400 mg
Epigallocatechine gallate (EGCG)
Gallocatechine gallate (GCG)
Epicatechine gallate (ECG)
Effect of green tea extract on obese women365
Inc., St. Charles, MO, USA). This kit employs the double-
antibody/polyethylene glycol technique using125I-labeled
adiponectin and a multispecies adiponectin rabbit antise-
rum. Plasma insulin levels were measured using a commer-
cially available radioimmunoassay (Linco Research, Inc., St.
Charles, MO, USA). The intra- and inter-assay coefficients of
variation were 3.1 and 4.9%, respectively. The limit of sen-
sitivity was 0.5 ng/ml. Plasma ghrelin levels were measured
with a commercially available radioimmunoassay (Linco
Research, Inc., St. Charles, MO, USA), using
ghrelin as a tracer. The detection limitation for the assay
was 10 ng/ml. The intra- and inter-assay coefficients of
variation were 6.5 and 9.6%, respectively.
EGCG dose analysis
The sample was extracted with 100 ml of 50% methanol in
sonication for 10 min. Then 2 ml of the extract were centri-
fuged at 10,000 rpm (Eppendorf Centrifuge 5402, MI, USA)
for 10 min. The supernatant was filtrated with a 0.22-mm
syringe filter (Millipore, Bedford, MA, USA), and 20 ml of
the filtrate were injected into the HPLC system. HPLC
analysis was performed by a Hitachi 7000 series module
equipped with a photodiode array detector and wavelength
was set at 273 nm. Catechin, epicatechin and EGCG were
separated from the extract using a Merck Purospher STAR
C-18 (50 ? 4.6 mm i.d., 5 mm). The flow rate of the mobile
phase was 0.8 ml/min. All samples were analyzed at room
temperature (25 ? 1?C).
The data were analyzed using SPSS software (version 11.5).
Student t-test was employed to examine the main out-
comes, demographic data, and other measurements be-
tween group means. Paired t-tests were utilized to
examine differences within group at 0e12 weeks. All p
values were two-tailed and the a level of significance was
set at 0.05. We estimated in power 0.8 that each group
needed 35 subjects.
Demographics and measurements at baseline
Among the 336 obese women screened at our outpatient
clinic, 100 fulfilled the inclusion and exclusion criteria and
were allocated equally into Groups A and B. The means (SD)
of age, height, BW and BMI were 43.4 (11.8) years, 158.2
(5.3) cm, 77.5 (12.5) kg and 30.8 (4.1) kg/m2, respectively.
Nine subjects of Group A and 13 subjects of Group B with-
drew due to personal reason. In the end, 78 patients com-
pleted the study (Fig. 1). As shown in Table 2, there was
no significant difference in the demographic and clinical
profiles of both groups prior to the study or in compliance
of dosage taken between the two groups.
Comparison between groups at 12 weeks
Table 2 displays the measurement after 12 weeks of inter-
vention. As can be seen, there was no statistical difference
in % reduction in BW, BMI and WC between the GTE and
placebo groups after 12 weeks of treatment. Comparison
between groups also showed no significant differences.
The average weight loss was 0.15 kg in the GTE group and
0.03 kg in the placebo group after 12 weeks of treatment.
Table 3 shows the % reduction in anthropometric mea-
sures, fasting serum levels and hormone factors. As can
be seen, there was no statistical difference in the % reduc-
tion between the two groups.
Comparison within group at 12 weeks
After treatment, the GTE group revealed significant re-
duction in WC, HC and levels of LDL-cholesterol and
triglyceride, and marked increase in the levels of HDL-
cholesterol, adiponectin and ghrelin. On the other hand,
the placebo group showed significant reduction in HC and
triglyceride only, and marked increase in the level of
No subjects withdrew from the study because of discomfort
or adverse effects associated with the treatment. Three
subjects developed mild constipation and two patients had
abdominal discomfort after GTE treatment, while two
subjects had mild constipation and one patient had ab-
dominal discomfort after cellulose treatment. All the
symptoms were noted in the first week after treatment.
No major adverse effects were noted.
The present initial results showed no statistical difference
in % reduction in BW, BMI and WC between the GTE and
placebo groups after 12 weeks of treatment. Moreover,
comparison between groups displayed no statistical differ-
ence in the levels of serum factors and hormone peptides.
This study found no effect of GTE weight reduction in
obese women. There was only a 0.3% reduction in BW
(0.15 kg) after 12 weeks of treatment with GTE. Chantre
and Lairon examined the effect of GTE (375 mg catechins
containing 270 mg EGCG; daily) on overweight subjects
and found a 4.6% reduction in BW.19However, their study
was not a controlled one. A randomized, double-blind con-
trolled study was conducted by Kovas et al. They investi-
gated the effect of GTE on maintaining body weight after
4 weeks of very-low-diet BW loss and found no significant
difference in BW regain between the GTE (573 mg catechins
containing 323 mg EGCG; daily) and placebo groups.27In
the present study, we used a similar daily dose of GTE
(491 mg catechins containing 302 mg EGCG; daily) on obese
women without any other weight control maneuvers. Our
study showed the same result. Many human studies showed
significant decrease in body weight and body fat18e24after
GTE intake. However, most of these studies were of short
duration,20e21had small sample sizes,20e23or were com-
bined with other weight control methods.
Despite showing no evidence supporting the effect of
GTT on weight reduction, the data of this study still
revealed the following. First, there were significant
366 C.-H. Hsu et al.
reductions in the levels of LDL-cholesterol and triglyceride
and marked increase in the level of HDL-cholesterol after
12 weeks of treatment in the GTE group. Animal studies
showed that GTE intake decreased the absorption of tri-
glycerides and cholesterol.28e29Some animal model studies
reported that GTE decreased plasma levels of LDL-
cholesterol and triglyceride and increased the level of
HDL-cholesterol.30e31The mechanism accounting for this
remains to be determined. An in vivo study might partly
explain the above finding that there was EGCG dose-
dependent inhibition of lipid accumulation in maturing pre-
adipocytes.12Although the human study of Nagao et al.
demonstrated that 12 weeks of GTE (690 mg catechins con-
taining 136 mg EGCG; daily) intake decreased the level of
malondialdehyde-modified LDL in men, neither their study
nor ours showed any significant difference in serum lipid or
blood sugar between the groups in the human studies. This
might be attributed to the dose of GTE being too low for
any effects to be detected. The optimum dose of GTE in-
take should be determined in order to detect its effect
on serum lipid in future human studies.
Second, the present study also aims to explore the
change in obesity-related hormone peptides after 12 weeks
of treatment. Although comparison between groups re-
vealed no significant difference in the level of hormone
peptides, the initial data showed increase in serum levels
of adiponectin and ghrelin in the GTE group after 12 weeks.
Adiponectin is a hormone produced in adipocytes. It has
been found that circulating adiponectin levels and adipo-
nectin gene expression in adipose tissue are reduced in pa-
tients with type 2 diabetes and obese populations.32e34
Many studies demonstrated that adiponectin has both
anti-atherogenic and anti-diabetic properties.32e37Some
animal studies have demonstrated that EGCG can increase
the level of adiponectin, which is a benefit biomarker.38e39
Kao et al. have reported that EGCG can significantly re-
duce the level of leptin and insulin in animal studies.40
However, this study could not obtain the same result. We
attributed this to the dose of GTE being too low for any ef-
fects to be detected in human studies. The effects of
EGCG on changes in hormone level and loss in body weight
vary with the route of administration. Oral intake of EGCG
Demographic and biochemical characteristics of participants at baseline and after 12 weeks
VariablesGreen tea extract (n Z 41), mean (SD) Placebo (cellulose)(n Z 37), mean (SD)
Baseline (A) 12 weeks (B)Difference
(A ? B)
Baseline (A)12 weeks (B) Difference
(A ? B)
Body mass index (kg/m2)
Waist circumflex (cm)
Hip circumflex (cm)
Systolic blood pressure
Diastolic blood pressure
82.9 (9.3)81.7 (9.1)1.2 (10.6)81.6 (11.5) 79.4 (10.9) 2.3 (10.4)
Fasting serum factors
Uric acid (mg/dl)
32.7 (18.8)29.8 (16.9)34.2 (33.3) 34.2 (33.0)2.9 (29.6)
5.7 (1.4)5.8 (1.5)
?0.007 (1.0)5.7 (1.4)5.6 (1.4)0.2 (1.1)
Leptin (ng /ml)
HOMA insulin resistance
*p Z 0.01e0.05; **p Z 0.001e0.01; ***p < 0.001.
Effect of green tea extract on obese women367
in animal studies showed less or no change in hormone
level and loss in body weight compared with the same
dose of EGCG injected.40The bioavailability and pharma-
cokinetics of EGCG in human studies merit further explora-
tion. Ghrelin is a novel growth hormone-releasing peptide
isolated mainly from the stomach.41It has been demon-
strated to alter feeding behavior, energy metabolism,
and gastrointestinal functions.42Many studies demon-
strated that weight loss was associated with increase in
ghrelin level.43e44Both groups in our study showed in-
creases in the level of ghrelin. This might imply that taking
GTE and cellulose would increase the secretion of hormone
peptides such as ghrelin, which might have potential ben-
efits on obese control. Further studies are needed to vali-
date such a possibility.
Finally, after 12 weeks of GTE treatment, serum EGCG
was detected in only five of 41 GTE samples. The reason
why serum levels of EGCG cannot be easily measured after
fasting overnight is worth further exploration. GTE have
many biological effects in vitro, and general effects are
observed in the range of 10e100 mM.45Healthy subjects
consuming 800 mg EGCG reached a plasma concentration
of 0.96 mM.46Our GTE subjects had daily oral intakes of
491 mg catechins containing 302 mg EGCG. This might ac-
count for the insignificant biological effect and why EGCG
was not detected in most of the serum samples. Moreover,
in a human study, single oral consumption of 800 mg EGCG
might cause mild headache and fatigue.46The bioavailabil-
ity and pharmacokinetics of EGCG in human and animal
models have been previously reported47e52How to deter-
mine the optimum EGCG dosage and achieve less adverse
effects is worth more in-depth investigation in future
It is impossible for all subjects to maintain the same food
consumption throughout the study period. The subjects
were not allowed to receive other obesity management and
were asked to keep their former diet during the study. We
expected that the randomized design could balance the
bias between the two groups. The biochemical data in both
groups, such as the triglyceride level, became different
after intervention. Whether it is due to the intake of GTE
and cellulose, or the change in eating habits of the subjects
during the study period merits further exploration.
Besides the trivial side effects, we had some interesting
observations, including the improvement of mild diarrhea
(two in the GTE group and one in the placebo group), and
insomnia (two in the GTE group). This might be verified with
larger samples and longer follow-up in the future.
This study showed no statistical difference in % reduction in
BW, BMI and WC between the GTE and placebo groups after
12 weeks of treatment. The intake of GTE (491 mg cate-
chins containing 302 mg EGCG) for 12 weeks is considered
safe in this study. The bioavailability and pharmacokinetics
of EGCG in human studies are worth more in-depth
Conflict of interest statement
None to declare.
We thank Yung-Jen Tsai and all colleagues in Taipei
Hospital, Taiwan, for their help with this study. This study
was supported financially by the National Science Council,
Taiwan under grant no. 95-2320-B-192-001. Clinical trial
registration no: NCT00383058.
% reduction in outcomes after 12 weeks of treatment
VariablesGreen tea extract
n Z 41, mean (SD)
n Z 37, mean (SD)
Body mass index (kg/m2)
Waist circumflex (cm)
Hip circumflex (cm)
Systolic blood pressure (mmHg)
Diastolic blood pressure (mmHg)
Fasting serum factors
Leptin (ng /ml)
HOMA insulin resistance index
368C.-H. Hsu et al.
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