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• 34 •Chin J Integr Med 2009 Feb;15(1):34-41
Obesity, a risk factor for many diseases, has
represented a prevalent tendency around the world,
especially in developed countries, such as Europe,
the United States and Japan(1). Diet-induced obesity
is generally considered due to excessive calorie
intake, decreased energy utilization and reduced
basal metabolism. In this type of obesity, either the
number or the size of fat cells shows a remarkable
increase because of the excessive storage of energy
consequent on the imbalance between energy
intake and expenditure(2). Excessive body fat may
trigger various chronic diseases that are called life-
style related diseases, such as hyperlipidemia,
hypertension and non-insulin dependent diabetes
mellitus, and increase the risk of coronary heart
disease(3). As a result, not only is one's quality of life
affected, but also his life span is shortened.
Variations in total energy intake and diet
composition are important in the regulation of
metabolic processes. Furthermore, dietary fat
promotes more effective fat storage in body than
dietary carbohydrate does. Consistent with these
suggestions, high fat diets may increase body weight
and cause adiposity in both humans and animals(4).
Thus, either inhibiting the digestion and absorption
of dietary fat or promoting fat oxidation is conducive
to treating obesity. Usually, dietary fat is not easily
absorbed from the intestine unless it has been
hydrolyzed by pancreatic lipase, so that gastric and
pancreatic lipases serve as the key enzymes for the
ORIGINAL ARTICLE
Beneficial Effects of Oolong Tea Consumption on Diet-induced
Overweight and Obese Subjects
HE Rong-rong (何蓉蓉)1, CHEN Ling (陈 玲)2, LIN Bing-hui (林炳辉)2,
MATSUI Yokichi (松井阳吉)3, YAO Xin-sheng (姚新生)1,4 and KURIHARA Hiroshi (栗原 博)4
1. School of Traditional Chinese Materia Medicine, Shenyang
Pharmaceutical University, Shenyang (110016), China; 2. Fujian
Institute of Traditional Chinese Medicine, Fuzhou (350003),
China; 3. Products Development Center, Suntory Ltd., 5-2-5,
Yamazaki, Shimamoto-cho, Mishima-gun, Osaka 618-0001,
Japan; 4. Institute of Traditional Chinese Medicine and Natural
Products, Jinan University, Guangzhou (510632), China
Correspondence to: Prof. KURIHARA Hiroshi, Tel:
86-20-85221352, E-mail: hiroshi_Kurihara@163.com
DOI: 10.1007/s11655-009-0034-8
ABSTRACT
ABSTRACT
Objective:
Objective:
To determine the anti-obesity effects of oolong tea on diet-induced overweight or
To determine the anti-obesity effects of oolong tea on diet-induced overweight or
obesity.
obesity.
Methods:
Methods:
A total of 8 g of oolong tea a day for 6 weeks was ingested by 102 diet-induced overweight
A total of 8 g of oolong tea a day for 6 weeks was ingested by 102 diet-induced overweight
or obese subjects. The body fat level of the subjects was determined at the same time by taking body weight,
or obese subjects. The body fat level of the subjects was determined at the same time by taking body weight,
height and waist measurements. The thickness of the subcutaneous fat layer was also determined on the
height and waist measurements. The thickness of the subcutaneous fat layer was also determined on the
abdomen 3 cm to the right of the navel by the ultrasonic echo method. On the other hand, effects of oolong
abdomen 3 cm to the right of the navel by the ultrasonic echo method. On the other hand, effects of oolong
tea ingestion on plasma triglyceride (TG) and total cholesterol (TC) were determined. Inhibitions of pancreatic
tea ingestion on plasma triglyceride (TG) and total cholesterol (TC) were determined. Inhibitions of pancreatic
lipase by oolong tea extract and catechins
lipase by oolong tea extract and catechins
in vitro
in vitro
were also determined.
were also determined.
Results:
Results:
A total of 70% of the severely
A total of 70% of the severely
obese subjects did show a decrease of more than 1 kg in body weight，including 22% who lost more than 3
obese subjects did show a decrease of more than 1 kg in body weight，including 22% who lost more than 3
kg. Similarly, 64% of the obese subjects and 66% of the overweight subjects lost more than 1 kg during the
kg. Similarly, 64% of the obese subjects and 66% of the overweight subjects lost more than 1 kg during the
experiment, and the subcutaneous fat content decreased in 12% of the subjects. The correlation between
experiment, and the subcutaneous fat content decreased in 12% of the subjects. The correlation between
weight loss and subcutaneous fat decrease in men (
weight loss and subcutaneous fat decrease in men (
r
=0.055) was obviously lower than that in women (
=0.055) was obviously lower than that in women (
r
=0.440,
=0.440,
P
<0.01). Body weight loss was significantly related to the decrease of the waist size in men (
<0.01). Body weight loss was significantly related to the decrease of the waist size in men (
r
=0.730,
=0.730,
P
<0.01)
<0.01)
and women (
and women (
r
=0.480,
=0.480,
P
<0.01). Also, the correlation between subcutaneous fat reduction and decreased waist
<0.01). Also, the correlation between subcutaneous fat reduction and decreased waist
size was significant in women (
size was significant in women (
r
=0.554,
=0.554,
P
<0.01), but not in men (
<0.01), but not in men (
r
=0.050,
=0.050,
P>
P>
0.05). Moreover, the plasma levels
0.05). Moreover, the plasma levels
of TG and TC of the subjects with hyperlipidemia were remarkably decreased after ingesting oolong tea for 6
of TG and TC of the subjects with hyperlipidemia were remarkably decreased after ingesting oolong tea for 6
weeks.
weeks.
In vitro
In vitro
assays for the inhibition of pancreatic lipase by oolong tea extract and catechins suggest that
assays for the inhibition of pancreatic lipase by oolong tea extract and catechins suggest that
the mechanism for oolong tea to prevent hyperlipidemia may be related to the regulative action of oolong tea
the mechanism for oolong tea to prevent hyperlipidemia may be related to the regulative action of oolong tea
catechins in lipoprotein activity.
catechins in lipoprotein activity.
Conclusions:
Conclusions:
Oolong tea could decrease body fat content and reduce body
Oolong tea could decrease body fat content and reduce body
weight through improving lipid metabolism. Chronic consumption of oolong tea may prevent against obesity.
weight through improving lipid metabolism. Chronic consumption of oolong tea may prevent against obesity.
KEY WORDS
KEY WORDS
oolong tea, overweight, obesity, cholesterol, triglyceride, pancreatic lipase
oolong tea, overweight, obesity, cholesterol, triglyceride, pancreatic lipase
• 35 •
Chin J Integr Med 2009 Feb;15(1):34-41
absorption of dietary fat. Of course, the absorption of
dietary fat from the intestine is also dependent on the
concerted action of other digestive lipases and bile(5, 6).
Oolong tea is mainly produced and consumed in
China, especially in South China. As one of popular
teas for the Chinese, oolong tea is traditionally
considered to have anti-obesity and hypolipidemic
effects. Recently, the pharmacological effects and
relative mechanisms of oolong tea have been studied
widely. For example, oolong tea could facilitate
lipid metabolism and prevent from obesity and fatty
liver in mice by the oral administration of a high-fat
diet for 10 weeks(7). Oolong tea fed orally to male
Sprague-Dawley rats for 30 weeks led to significant
suppression of body weights and decrease in the
levels of triglyceride (TG) and total cholesterol (TC)(8).
A study conducted in twenty patients with coronary
artery disease who consumed oolong tea (1 000 mL/
day) for one month shows that oolong tea resulted in
a significant increase of plasma adiponectin levels and
decrease in LDL particle size. A significant difference
in hemoglobin A1c levels (7.23±4.45%
vs
6.99±
4.30%,
P
<0.05) was also observed before and after
the intake of oolong tea(9-11).
On the bases of these findings, it is well
presumed that long-term consumption of tea may be
beneficial to the treatment of obesity. However, there
are few clinical studies in the effects of oolong tea on
diet-induced overweight and obesity. In the present
study, a clinical trial was performed to determine the
anti-obesity effects of oolong tea.
METHODS
Selection Criteria
The subjects were selected according to
the World Health Organization (WHO) obesity
classification system based on the average adult
body mass index (BMI; WHO, 1990), which is an
international standard(12). These subjects were then
classified into three types using cut-off points for the
definition of obesity introduced by the WHO in 1995(13)
and 1997(14): within 25<BMI<30, indicating overweight
or preobesity (Ⅰ); 30<BMI<35, indicating obesity (Ⅱ);
and 35<BMI, indicating severe obesity (Ⅲ). Pregnant
women, nursing mothers, people who habitually drink
tea served from more than 4 g of leaf tea per day and
individuals with secondary obesity induced by various
diseases or drugs were excluded.
Subjects
A total of 102 Chinese subjects, including 42
males and 60 females, aged 18 to 65 years with
diet-induced overweight and obesity were recruited
from the general population of Fuzhou city. The
ages and body weight levels of the 102 subjects are
shown in Table 1. All volunteers were selected by
initial screening based on questionnaires related
to their diet, physical activity, family and personal
health histories, and availability for participation.
A cooperating physician performed a general
medical evaluation, and the height and weight were
recorded.
Table 1. Age Group and Weight Classification of
Subjects before Oolong Tea Treatment (Case)
No. of
subjects
Age layer
Weight
classification
by BMI
<30 -30 -40 -50 -65 ⅠⅡⅢ
102 5 12 33 37 15 52 44 6
The cause of being overweight and obese among
the subjects is ascribed as an imbalance between energy
intake and expenditure. A researcher explained the
purpose of the experiment, test protocol and bioactivity
of oolong tea prior to the experiment to all subjects.
Then, informed consent to participate in this study was
obtained. All subjects were given their informed consent
to participate in the study, which was approved by the
Medical Ethics Committee of the Fujian Institute of
Traditional Chinese Medicine, and was performed in
accordance with the Helsinki Declaration. All volunteers
signed for their informed consent. Clinical testing was
carried out in medical facilities of the Fujian Institute of
Traditional Chinese Medicine (Fuzhou, China).
Experimental Protocol
Oolong tea packed in a 2-g bag was provided
by the Fujian Tea Import and Export Co., Ltd. (China).
The tea was brewed by adding 300 mL of boiling
water to a glass container containing the tea bag.
The tea was then steeped for 5 min before intake. It
was ingested twice in the morning and twice in the
afternoon, so that the subjects received 4 servings of
tea bags daily for a total of 8 g a day for 6 weeks.
The protocol was explained to each subject, and
the intake of various anti-obesity drugs, black tea and
green tea was prohibited throughout the test period.
There was no further restriction on meals or daily life
except for the prohibition of intensive exercise.
• 36 •Chin J Integr Med 2009 Feb;15(1):34-41
Measurements of Body Weight, Height, Waist,
Thickness of the Subcutaneous Fat Layer
The body fat level of subjects was determined
before and on the final day of the experiment from 9:00
to 11:00 a.m. by taking body weight, height and waist
measurements. The thickness of the subcutaneous fat
layer was also determined on the abdomen 3 cm to
the right of the navel by the ultrasonic echo method.
Adverse Reaction
Safety was evaluated as follows: safe (no adverse
effects); borderline (slight adverse effects, but safe
to continue); and unsafe (adverse effects, ingestion
discontinued). The test director was instructed to report
cases with serious adverse events related to the test,
and the director was responsible in deciding whether to
discontinue testing after consultation with the subject
who had serious adverse effects related to the testing.
Measurement of Plasma TG and TC
Plasma TG and TC levels in the 102 overweight
and obese subjects were respectively measured before
the treatment initiation as the baseline levels, and the
subjects with high plasma TG or high plasma TC were
monitored on the final day of the experiment. Blood
samples were collected in the morning after fasting
from 21:00 on the previous day into a tube containing
2% sodium heparin. Then, each tube was centrifuged
at 3 000 r/min for 5 min to obtain the supernatant. All
samples were stored at -20 ℃ until the assay of plasma
TG and TC was performed by colorimetric analysis
using triglyceride E-test and total cholesterol E-test kits
(Wako Pure Chemical Industries, Ltd.).
Catechins and Caffeine Analysis
A tea bag containing 2 g of oolong tea was
brewed by adding 300 mL of boiling water to a
glass container, followed by 5-min steeping. The
concentrations of caffeine, gallic acid, flavanols, and
other polyphenols in the oolong tea extract were
analyzed by high-performance liquid chromatography
[HPLC, column: Cosmosil 5PE-MS (Nakalai Tesuque,
Kyoto, Japan, 4.6 x 150 mm, 5 μm), mobile phase:
eluent A: 0.05% trifluoroacetic acid (TFA) in water;
eluent B: 0.05% TFA in acetonitrile using a gradient
program of eluent B content: 10% for 5 min, 21%
for 8 min, 90% for 1 min, and 90% for 6 min,
flow rate: 2 mL/min with ultra-violet spectroscopy
detection at 280 nm and 40 ℃(15)]. The quantification
of caffeine, gallic acid and flavanols was performed
using standard calibration curves of their respective
reagent grade compounds. Other polyphenols were
quantified using a calibration curve derived from other
polyphenols that had been isolated from tea by HPLC.
The components of caffeine and tea polyphenols of
oolong tea are shown in Table 2.
Table 2. Components of Caffeine and
Polyphenols in Oolong Tea
Components Oolong tea (mg/100 mL)
Gallic acid 2.19
Caffeine 23.51
Gallocatechine 6.68
Epigallocatechine 16.14
Catechine 1.65
Epicatechine 5.08
Epigallocatechine gallate 25.73
Allocatechine gallate 1.85
Epicatechine gallate 5.73
Catechine gallate 0.60
Polymerized 33.65
Note: The data are mean amounts of oolong tea components
consumed daily
Measurement of Pancreatic Lipase Activity
in
vitro
Oolong tea was extracted with 15 volumes of
boiling water for 5 min. After filtration and evaporation,
the recovered residue was powdered under frozen-
decompression conditions. The recovery rate was
12.1%, and the extract was then used for the experiment.
(±)-catechin, (-)-epigallocatechin-3-gallate (EGCG),
(-)-epicatechin-3-gallate (ECG), (-)-gallocatechin gallate
(GCG), (-)-gallocatechin (GC) and (-)-catechin gallate
(CG) were purchased from the Sigma Chemical Co.,Ltd,
and used as a positive control. Pancreatic lipase activity
was measured using 4-methylumbelliferyl oleate (4-MU
oleate) as a substrate.
Pancreatic lipase (Type Ⅵ-S, from porcine
pancreas) and 4-MU oleate were purchased from the
Sigma Chem. Co., respectively. A total of 25 mL of
tea extract solution dissolved in water and 50 μL of
0.1 mmol/L 4-MU oleate solution dissolved in a buffer
consisting of 13 mmol/L Tris-HCl, 150 mmol/L NaCl, and
1.3 mmol/L CaCl2 (pH 8.0) were mixed in the well of a
microtiter plate, and then 25 μL of the lipase solution
(50 U/mL) in the buffer was added to start the enzyme
reaction. After incubation at 25 ℃ for 30 min, 0.1 mL of
0.1 mol/L sodium citrate (pH 4.2) was added to discontinue
the reaction. The amount of 4-methylumbelliferone
• 37 •
Chin J Integr Med 2009 Feb;15(1):34-41
released by the lipase was measured with a fluorometrical
microplate reader (Fluoroskan Ascent, LabSystems
Inc.) at an excitation wavelength of 355 nm and an
emission wavelength of 460 nm(16). The 50% inhibitory
concentration (IC50) of each test sample was obtained
from the least-squares regression line of the plots of the
logarithm of the sample concentration (log) versus the
pancreatic lipase activity (%)(17).
Statistical Analysis
Statistical analysis of data was performed using
SPSS 13.0 statistical package. One-Way analysis of
variance (ANOVA) was applied to analyze for difference
in data of biochemical parameters among the different
groups, followed by Dunnett's significant post-hoc test
for pair-wise multiple comparisons. Differences were
considered to be significant when the probability value
was less than 0.05, and the results were expressed
as the means ± standard deviation. The effect of
oolong tea on overweight or obese subjects was also
examined with regard to body weight, waist size and
subcutaneous fat thickness.
RESULTS
Effects of Oolong Tea Ingestion on Overweight
and Obese Subjects
The correlation coefficient between height and
weight for the 102 subjects with diet-induced obesity
before the ingestion of oolong tea was
r
=0.261 (Figure
1A), and their average weight was 74.1±8.2 kg. After
ingestion for 6 weeks, the average weight decreased
to 71.2±8.1 kg, and the correlation coefficient
between height and weight also increased (
r
=0.620)
as shown in Figure1B. These results show that oolong
tea ingestion slightly improved diet-induced obesity.
The average weight changed from 79.7±6.7 kg to
76.1±7.5 kg in men (Figure 1C and 1D), and from
70.2±6.8 kg to 67.8±6.7 kg in women (Figure 1E and
1F). From the above results, the treatment appeared
to be more effective in women.
The degree of changes before and after oolong
tea ingestion was observed in terms of fat thickness,
weight and waist. The correlation coefficient between
the decreases in weight and subcutaneous fat (fat
thickness) in all subjects was
r
=0.140 (Figure 2A),
and was correlated between them. The weight loss
in males did not directly correlate with a decrease
in subcutaneous fat (
r
=0.055, Figure 2B). However,
in women, it was significantly correlated (
r
=0.440,
P
<0.01, Figure 2C). Although the waist size was only
slightly decreased (average of 2.58 cm), the decrease
was directly correlated with the weight loss (
r
=0.480,
P
<0.01, Figure 3C). The correlation between the
decreases in subcutaneous fat and waist size was
more marked in women (Figure 4C,
r
=0.554,
P
<0.01)
than in men (Figure 4B,
r
=0.050).
After the ingestion of oolong tea for 6 weeks,
70% of the severely obese subjects show decreased
Figure 1. Effects of Oolong Tea Ingestion on the Correlation Coefficient between Weight and Height (102 cases)
Notes: A: all volunteers before the ingestion of oolong tea; B: all volunteers after the ingestion of oolong tea; C: male subjects
before the ingestion of oolong tea; D: male subjects after the ingestion of oolong tea; E: female subjects before the ingestion of oolong
tea; F: female subjects after the ingestion of oolong tea
110
Weight (kg)
Height (cm)
F
90
70
50
150 160 170 180 190
y=0.63x-31.80
r
=0.550,
P
<0.01
110
Weight (kg)
110
Weight (kg)
110
Weight (kg)
Height (cm)
A
90
70
50
150 160 170 180 190
y=0.43x+8.04
r
=0.260,
P
<0.01
110
Weight (kg)
Height (cm)
B
90
70
50
150 160 170 180 190
y=0.74x-49.24
r
=0.620,
P
<0.01
Height (cm)
C
90
70
50
150 160 170 180 190
Height (cm)
D
90
70
50
150 160 170 180 190
y=0.55x-15.95
r
=0.300,
P
<0.1
110
Weight (kg)
Height (cm)
E
90
70
50
150 160 170 180 190
y=0.61x-26.90
r
=0.530,
P
<0.01
y=0.43x+8.04
r
=0.260,
P
<0.1
• 38 •Chin J Integr Med 2009 Feb;15(1):34-41
body weight of more than 1 kg, including 22% with
more than 3 kg loss. Similarly, 64% of the obese
subjects as well as 66% of the overweight ones lost
more than 1 kg of body weight (Figure 5).
Effects of Oolong Tea Ingestion on Plasma TG
and TC Levels
The plasma TG of 22 subjects and the plasma TC
of 51 subjects were over the normal level before the
ingestion of oolong tea. After the ingestion of oolong
tea for 6 weeks, the plasma TG level of the 22 subjects
with hypertriglyceridemia decreased about 20%
Figure 2. Effect of Oolong Tea Ingestion on the Correlation Coefficient
between Weight and Subcutaneous Fat (102 cases)
Notes: Δ(delta): The degree of change before and after oolong tea ingestions. A: all volunteers after the ingestion of oolong tea; B:
male subjects after the ingestion of oolong tea; C: female subjects after the ingestion of oolong tea; the same as in Figures 3 and 4
△Fat thickness (mm)
△Weight (kg)
25
20
15
10
5
0
03691215
A
y=0.27x+6.02
r
=0.140,
P
<0.2
△Fat thickness (mm)
△Weight (kg)
△Fat thickness (mm)
△Weight (kg)
25
20
15
10
5
0
0 3 6 9 12 15
B
y=-0.12x+8.26
r
=0.055,
P
>0.05
25
20
15
10
5
0
03691215
C
y=0.81x+3.92
r
=0.440,
P
<0.01
Figure 3. Effect of Oolong Tea Ingestion on the Correlation Coefficient
between Weight and Waist Size (102 cases)
△Waist (cm)
△Weight (kg)
A
y=0.42x+2.80
r
=0.440,
P
<0.01
12
9
6
3
0
△Waist (cm)
△Weight (kg)
C
y=0.52x+2.56
r
=0.480,
P
<0.01
12
9
6
3
0
03691215
△Waist (cm)
△Weight (kg)
B
y=0.66x+1.44
r
=0.730,
P
<0.01
12
9
6
3
0
0 3 6 9 12 1503691215
Figure 4. Effect of Oolong Tea Ingestion on the Correlation Coefficient
between Waist and Subcutaneous Fat (102 cases)
△Fat thickness (mm)
△Waist (cm)
25
20
15
10
5
0
02.55 7.5
10
C
y=
0.96x+2.38
r
=0.554,
P
<0.01
△Fat thickness (mm)
△Waist (cm)
25
20
15
10
5
0
0 2.5 5 7.5 10
A
y=
0.39x+5.24
r
=0.190,
P
<0.1
△Fat thickness (mm)
△Waist (cm)
25
20
15
10
5
0
0 2.5 5 7.5 10
B
y
=
0.12x+7.37
r
=0.050,
P
>0.05
Figure 5. Beneficial Effects of Oolong Tea
Ingestion for Diet-induced Overweight and
Obese Subjects (102 cases)
Degree of obesity
58
52
50
48
15
8
14
22
33
34
36
30
1% 50% 100% >3 kg
1-3 kg
<1 kg
severe
moderate
slight
total
• 39 •
Chin J Integr Med 2009 Feb;15(1):34-41
and energy expenditure(18). Therefore, promoting fat
metabolism should be considered as basic. It was
previously reported that oolong tea could accelerate fat
metabolism through activating the lipoprotein lipase(19),
and significantly increase energy expenditure and fat
oxidation(9). In general, the main active components of
oolong tea affecting lipid metabolism are thought to be
tea caffeine and tea polyphenols including EGCG, EGC,
ECG, GCG, GC, CG and EC(20, 21). Among these active
components, caffeine played a key role for oolong tea
to prevent or treat obesity because of its thermogenesis
and fat oxidation effects. Some evidence from the high-
fat diet-treated mice indicated that the caffeine isolated
from oolong tea could enhance noradrenaline-induced
lipolysis. As a non-specific antagonist of adenosine
receptors, caffeine modifies energy metabolism through
increasing intracellular free Ca2+ concentration and
promoting catecholamine release from noradrenergic
nerve terminal. Caffeine also elevates the metabolic
rate and fatty acid availability by means of lipolysis of
fat cells(22, 23). The effects of caffeine are ascribed to
the adenyl cyclase-cAMP phosphodiesterase cycle(24).
cAMP-dependent protein kinase A activates hormone-
sensitive lipase, and then this enzyme catalyzes the
hydrolysis of TG in fat cells so that eventually lipolysis
is enhanced(25, 8). Besides, catechins and EGCG were
also proven to reduce the total TG accumulation of
murine 3T3-L1 preadipocytes during their differentiation
into adipocytes induced by dexamethasone, 1-methyl-
3-isobutylxanthine and insulin(26). EGCG and ECG
inhibited acetyl-CoA carboxylase activity, a rate-
limiting step in the fatty acid biosynthesis pathway, in
3T3-L1 cells(27).Therefore, the
in vitro
effect of EGCG
on fat tissues may be mediated by the modulation of
hormone-stimulated cell proliferation and differentiation
or by the inhibition of fat cell functions(6).
Reducing glucose and fat absorption were known
as an important step to improve obesity(28). It was
Table 3. Inhibition of Pancreatic Lipase by
Oolong Tea Extract and Catechins
in vitro
Sample Lipase inhibitory activity (IC50, μg/mL)
Oolong tea extract 0.97
Catechin >10
EGCG 0.16
ECG 0.14
GCG 0.24
GC >10
CG 0.38
Note: The values are presented as the mean of four
samples
Inhibition of Pancreatic Lipase by Oolong Tea
Extract and Catechins
in vitro
The IC50 values of oolong tea extract and tea
polyphenols such as catechin, EGCG, ECG, GCG, GC and
CG were shown in Table 3, indicating that ECG and EGCG
caused more potent inhibition than the oolong tea extract
did. GCG and CG had weakly inhibitory effects. However,
catechin and GC were not effective at up to 10 μg/mL.
DISCUSSION
In the present study, 102 diet-induced overweight
and obese subjects were recruited to investigate the
anti-obesity effects of oolong tea. Each of the subjects
ingested 8 g per day of oolong tea for 6 weeks. The
results show that the correlation between height and
body weight was slightly improved, which was more
remarkable in women. Although the effect of oolong tea
was slight or moderate, it was interesting that oolong
tea led to the drop of body weight reduction without
significant changes in food consumption before and
after the ingestion of oolong tea.
Furthermore, the waist size in the obese subjects
was observed to appear slightly lower after 6-week
ingestion of oolong tea, and the correlation coefficient
between the decrease in waist size and the decrease
in subcutaneous fat thickness was more marked in
women (
r
=0.554) than in men (
r
=0.050), indicating the
decrease in waist size in men might be due to improved
internal adipose levels rather than subcutaneous ones.
Usually, the general obesity is defined as an
excessive amount of fat tissue in the body, which
results from an imbalance between energy intake
(
P
<0.05, Figure 6A). and the plasma TC level in the
subjects with hypercholesterolemia also significantly
decreased (
P
<0.01, Figure 6B).
TG (mg/dL)
350
250
150
Before treatment After treatment
280
260
240
220
TC (mg/dL)
Before treatment After treatment
Figure 6. Effects of Oolong Tea Ingestion on
Plasma TG and TC Levels
Notes: A: 22 subjects with high plasma TG level; B: 51
subjects with high plasma TC level;
P
<0.05,
P
<0.01
AB
• 40 •Chin J Integr Med 2009 Feb;15(1):34-41
found that polyphenols, including catechins, in oolong
tea could inhibit some digestive enzymes such as
α-glucosidase, which may be related to the inhibitory
effect of oolong tea on the absorption of glucose and
sucrose(28). However, it is not likely that the suppressive
effect of oolong tea on body weight is completely
dependent on a reduction in carbohydrate absorption.
Other studies displayed that oolong tea suppressed
the intestinal absorption of dietary fat by inhibiting
pancreatic lipase(7, 29). Our results also proved that
oolong tea extract and catechins inhibited pancreatic
lipase
in vitro
, in which ECG and EGCG caused more
potent inhibition than the oolong tea extract did. Thus,
the anti-obesity effects of oolong tea were not due to
diarrhea or anorexia, but to promoting lipid utilization
induced by caffeine, the suppression for fat tissue
function induced by catechins as mentioned above,
and the control of lipid absorption from the intestine.
A correlation between obesity and
hyperlipidemia crisis has been previously confirmed
and excessive cholesterol in obese subjects causes
arteriosclerosis(30-32). Therefore, it is important to
keep plasma TG and cholesterol at normal levels for
the prevention of diseases such as arteriosclerosis,
cerebral apoplexy and myocardial infarction. In
the present study, it was observed that oolong tea
decreased the plasma TG level to 20% in 22 subjects
with obesity and improved the plasma TC level
in 51 obesity subjects. However, the mechanism
responsible for the antihyperlipidemic effects of
oolong tea remains unclear. Many studies on the
reduction of cholesterol levels induced by tea have
been conducted in Japan since the 1980s. It has been
proved that tea catechins not only inhibit cholesterol
absorption by intestinal epithelium cells(33) and
decrease the solubility of cholesterol in bile acid(34, 35)
but also activate lipoprotein lipase to reduce the levels
of cholesterol and TG in the blood via the hydrolysis
of TG in TG-rich lipoprotein(19). Tea catechins also
improve the balance between high density lipoprotein
cholesterol (HDL) and low density lipoprotein
cholesterol (LDL)(36). TC, LDL and TG levels in the
plasma are decreased in healthy subjects, whereas
HDL levels in hyperlipidemia subjects are increased
by the ingestion of oolong tea(37). These data suggest
that the mechanism for oolong tea to prevent
hyperlipidemia may be related to the regulative action
of oolong tea catechins including EGCG, EGC, ECG,
GCG, GC, CG and EC in lipoprotein metabolism.
Although we are unable to describe the mechanism
responsible for plasma TC metabolism, it was
previously noted that this effect is due to inhibition of
the synthesis of cholesterol in the liver(38).
The increased risk of life-style related diseases
in obese individuals has been known since the ancient
times(39). The present study shows that oolong tea has
beneficial effects on health such as anti-obesity activity
and the improvement of lipid metabolism, in which its
consumption moderately reduces body weight and
decreases body fat contents. As a result, continuous
consumption of oolong tea may prevent many diseases
related to obesity from occurring without adversely
suppressing a person's appetite or physical fitness.
REFERENCES
Abelson P, Kennedy D. The obesity epidemic. Science
2004;304:1413.
Hill JO, Melanson EL, Wyatt HT. Dietary fat intake and
regulation of energy balance: Implications for obesity. J
Nutr 2000; 130: 284S-288S.
Manson JE, Colditz GA, Stampfer MJ, Willett WC, Rosner
B, Monson RR, et al. A prospective study of obesity and
risk of coronary heart disease in women. N Engl J Med
1990;322:882-889.
Astrup A, Buemann B, Western P, Toubro S, Raben A,
Christensen NJ. Obesity as an adaptation to a high-fat
diet: evidence from a cross-sectional study. Am J Clin Nutri
1994;59:350-355.
Campfield LA, Smith FJ, Burn P. Strategies and potential
molecular targets for obesity treatment. Science 1998;
280:1383-1387.
Bray GA, Greenway FL. Current and potential drugs for
treatment of obesity. Endocr Rev 1999;20:805-875.
Han LK, Takaku T, Li J, Kimura Y, Okuda H. Anti-obesity
action of oolong tea. Int J Obes 1999;23:98-105.
Kuo KL, Weng MS, Chiang CT, Tsai YJ, Lin-Shiau SY, Lin
JK. Comparative studies on the hypolipidemic and growth
suppressive effects of oolong, black, pu-erh, and green tea
leaves in rats. J Agric Food Chem 2005; 53:489-489.
Rumpler W, Seale J, Clevidence B, Judd J, Wiley E,
Yamamoto S, et al. Oolong tea increases metabolic rate
and fat oxidation in men. J Nutr 2001;131:2848-2852.
Okuda H, Han LK. Medicinal plant and its related metabolic
modulators. Nippon Yakurigaku Zasshi 2001;118:347-351.
Davies MJ, Judd JT, Baer DJ, Clevidence BA, Paul DR,
Edwards AJ, et al. Black tea consumption reduces total and
LDL cholesterol in mildly hypercholesterolemic adults. J
Nutr 2003;133:3298-3302.
Khosla T, Lowe CR. Indices of obesity derived from body
weight and height. Br J Prev Soc Med 1967;21:122-128.
WHO Physical Status: The use and interpretation of
anthropometry. Report of a WHO expert committee
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
11.
12.
13.
• 41 •
Chin J Integr Med 2009 Feb;15(1):34-41
Geneva: World Health Organization Technical Report
Seriels; 1995:854.
WHO. Obesity: preventing and managing the global
epidemic. Report of a WHO Consultation on obesity,
Geneva 3-5, June 1997. World Health Organization
Techinical Report Series. Vol. 210. Geneva: World Health
Organization;1997:1-276.
Xie B, Shi H, Chen Q, Ho CT. Antioxidant properties of
fractions and polyphenol constituents from green, oolong
and black teas. Proc Natl Sci Counc Repub China (B)
1993;17:77-84.
Bitou N, Ninomiya M, Tsujita T, Okuda H. Screening of
lipase inhibitors from marine algae. Lipids 1999;34:441-445.
Golor G, Yamashita K, Koner W, Hagenmaier H, Neubert
D. Kinetics and inductive potency of 1, 2, 3, 4, 6, 7,
8-heptachlorodibenzo-p-dioxin (H7CDD) in rats. Life Sci
2001;69:493-508.
Saris W. Sugars, energy metabolism, and body weight
control. Am J Clini Nutri 2003;78:850-857.
Iwata K, Inayama T, Miw S, Kawaguchi K, Koike G. Effect of
oolong tea on plasma lipids and lipoprotein lipase activity in
young women. J Jpn Soc Nutr Food Sci 1991;44:251-259.
Lin YS, Tsai YJ, Tsay JS, Lin JK. Factors affecting the
levels of tea polyphenols and caffeine in tea leaves. J Agric
Food Chem 2003;51:1864-1873.
Dulloo AG, Dure C, Rohrer D, Girardier L, Mensi N, Fathi M.
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 Nutri 1999;70:1040-1045.
Bianchi CP. Cellular pharmacology of contraction
of skeletal muscle. In: Narahashi T, ed. Cellular
pharmacology of excitable tissues. Charles C: Thomas
Publisher;1975:485-519.
Arciero PJ, Gardner AW, Calles-Escandon J, Benowitz NL,
Poehlman ET. Effects of caffeine ingestion on NE kinetics,
fat oxidation, and energy expenditure in younger and older
men. Am J Physiol 1995;268:E1192-E1198.
Couturier C, Janvier B, Girlich D, Bereziat G, Andreani-
Mangeney M. Effects of caffeine on lipoprotein lipase gene
expression during the adipocyte differentiation process.
Lipids 1998;33:455-460.
Mulder H, Holst LS, Svensson H, Degerman E, Sundler
F, Ahren B. Hormone-sensitive lipase, the rate-limiting
enzyme in triglyceride hydrolysis, is expressed and active
in beta-cells. Diabetes 1999;48: 228-232.
Kao YH, Hiipakka RA, Liao S. Modulation of obesity by
green tea catechins. Am J Clin Nutr 2000;72:1232-1233.
Watanabe J, Kawabata J, Niki R. Isolation and
identification of acetyl-CoA carboxylase inhibitors from
14.
15.
16.
17.
18.
19.
20.
21.
22.
23.
24.
25.
26.
27.
green tea (Camellia sinensis). Biosci Biotechnol Biochem
1998;62:532-534.
Nakahara K, Izumi R, Kodama T, Kiso Y, Tanaka T.
Inhibition of postprandial hyperglycaemia by oolong tea
extract (OTE). Phytother Res 1994;8:433-435.
Han LK, Kimura Y, Kawashima M, Takaku T, Taniyama
T, Hayashi T, et al. Anti-obesity effects in rodents
of dietary teasaponin, a lipase inhibitor. Int J Obes
2001;25:1459-1464.
Inui Y, Kawata S, Matsuzawa Y, Tokunaga K, Fujioka A,
Tamura S, et al. Increased level of apolipoprotein B mRNA
in the liver of ventromedial hypothalamus lesioned obese
rats. Biochim Biophys Res Commun 1989;163:1107-1112.
Wang SR, Infante J, Catala D, Petit D, Bonnefis MT, Infante
R. Lipid and lipoprotein synthesis in isolated and cultured
hepatocytes from lean and obese Zucker rats. Biochim Acta
1989;1002:302-311.
Garrison RJ, Wilson PW, Castelli WP, Feinleib M,
Kannel WB, McNamara PM. Obesity and lipoprotein
cholesterol in the Framingham offspring study. Metabolism
1980;29:1053-1060.
Chisaka T, Matsuda H, Kubomura Y, Mochizuki M,
Yamahara J, Fujimura H. The effect of crude drugs on
experimental hypercholesteremia: Mode of action of
(-)-epigallocatechin gallate in tea leaves. Chem Pharm Bull
1988;36:227-233.
Ikeda I, Imasato Y, Sasaki E, Nakayama M, Nagao T,
Takeo T, et al. Tea catechins decrease micellar solubility
and intestinal absorption of cholesterol in rats. Biochim
Biophys Acta 1992;1127:141-146.
Okuda T, Kimura Y, Yoshida T, Hatano T, Okuda H, Arichi S.
Studies on the activities of tannins and related compounds
from medicinal plants and drugs. I. Inhibitory effects on lipid
peroxdation in mitochondria and microsomes of liver. Chem
Pharm Bull 1983;31:1625-1631.
Muramatsu K, Fukuyo M, Hara Y. Effect of green tea
catechins on plasma cholesterol level in cholesterol-fed
rats. J Nutr Sci Vitaminol 1986;32:613-622.
Matsuda H, Chisaka T, Kubomura Y, Yamahara J, Sawada
T, Fujimura H. Effects of crude drugs on experimental
hypercholesterolemia. I. Tea and its active principles. J
Ethnopharmacol 1986;17:213-224.
Hasegawa N, Yamda N, Mori M. Powdered green tea
has antilipogenic effect on Zucker rats fed a high-fat diet.
Phytother Res 2003;17:477-480.
Matsuzawa Y. Life style-related disease. Nippon Rinsho
2001;59:188-194.
(Received September 17, 2008)
Edited by WANG Wei-xia
28.
29.
30.
31.
32.
33.
34.
35.
36.
37.
38.
39.
