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Pediatric Diabetes 2012: 13: 572– 577
doi: 10.1111/j.1399-5448.2012.00877.x
All rights reserved
©2012 John Wiley & Sons A/S
Pediatric Diabetes
Original Article
Further increase of obesity prevalence
in Chinese children and adolescents –
cross-sectional data of two consecutive samples
from the city of Shanghai from 2003 to 2008
Zhang M, Guo F, Tu Y, Kiess W, Sun C, Li X, Lu W, LUO F. Further
increase of obesity prevalence in Chinese children and adolescents –
cross-sectional data of two consecutive samples from the city of Shanghai
from 2003 to 2008.
Pediatric Diabetes 2012: 13: 572–577.
Objective: Putative changes in the prevalence of obesity in Chinese children
and adolescents in Shanghai, one of the most urbanized areas in China, were
analyzed in a cross-sectional manner in 2003–2008.
Methods: One urban and one suburban district were randomly selected.
70 582 students in 2003 and 86 355 students in 2008 from schools from within
the two districts were examined. Anthropometric parameters were measured
in all. Adiposity status was estimated using body mass index according to
International Obesity Task Force standards. The prevalence of obesity was
analyzed.
Results: The standardized prevalence of overweight significantly increased
from 12.75 to 14.2% (p <0.01), and the prevalence of obesity significantly
increased from 3.35 to 3.94% (p <0.01) during the study period. In contrast to
data from developed countries, the prevalence of obesity decreased with age in
both boys and girls. The prevalence of obesity and overweight in boys was
significantly higher than that in girls (p <0.01). Interestingly, the prevalence
of overweight and obesity in the urban area was also significantly higher than
that in suburb area (p <0.01).
Conclusion: Over a 5-yr period, there was a significant increase in the
prevalence of obesity in children and adolescents in Shanghai. The high
percentage of overweight and obesity in the young age groups is of particular
concern. Urbanization might be a causative factor for the increase in obesity
prevalence in Chinese children in the Shanghai area.
Miaoying Zhanga, Fengxia
Guob, Yuezhen Tuc,
Wieland Kiessd, Chengjun
Suna,XiLi
a,WeiLu
aand
Feihong LUOa
aDepartment of Pediatric
Endocrinology and Inborn Metabolic
Diseases, Children’s Hospital of Fudan
University, Shanghai, China;
bDepartment of Health education, The
Center of Disease Control and
Prevention in Xuhui District, Shanghai,
China; cDepartment of Health
education, The Center of Disease
Control and Prevention in Minhang
District, Shanghai, China; and
dDepartment of Women and Child
Health, Hospital for Children and
Adolescence, University of Leipzig,
Leipzig, Germany
Key words: childhood – epidemiology
–obesity
Corresponding author:
Feihong LUO
Department of Pediatric
Endocrinology and Inborn Metabolic
Diseases
Children’s Hospital of Fudan
University
Shanghai, China
Tel: +86-21-64931226
fax: +86-21-64931901
e-mail: luofh@fudan.edu.cn
Submitted 2 December 2011.
Accepted for publication 12 April
2012
A recent study in China indicated that 9.7% of the
adult population had type 2 diabetes and 15.5% had
pre-diabetes (1). The prevalence of type 2 diabetes
is expanding more rapidly in Asian than in Western
countries, this is particularly so in younger age groups
(2). In addition, a strong association between high
572
Obesity Shanghai trend in Chinese children
body mass index (BMI) during childhood and obesity
during adult life has been established (3–5).
Obesity may be caused by excessive energy intake
and lack of physical activity. In addition, both genetic
and socioeconomic factors may contribute to the
development of overweight and obesity already at a
young age. The increasing prevalence of obesity in the
young is being recognized as a serious public health
concern due to its tight association with obesity and
its co-morbidities in adults. At present, a few countries
are experiencing a plateauing prevalence of overweight
and obesity in children and adolescents albeit at a high
level (6–8). However, in most countries obesity rates
are still increasing rapidly. From the 1970s to the end
of the 1990s, the school-age prevalence of overweight
and obesity has doubled or even tripled in several large
countries (9).
Shanghai is one of the largest metropolitan areas
in China and a leading economic region. The rapid
development in Shanghai over the past two decades
resulted in a dramatic change in life style in the
Shanghai population. This might very well have an
impact on the obesity prevalence in children and
adolescents. However, no study to date has investigated
the prevalence of childhood obesity in Shanghai. In
this study, we therefore aimed to provide data on the
prevalence of overweight and obesity among children
and adolescents in two consecutive cross-sectional
cohorts in Shanghai during a 5-yr period between
the year 2003 and 2008.
Methods
Study population
There are 19 districts in Shanghai, 9 of which are
urban and 10 are suburban. The determination of
urban or suburban was determined according to the
traditional geographical distribution and the data on
the gross domestic product per capita available in
the Statistical Yearbook of Shanghai. In 2003, we
randomly selected one district from the urban area
and one from a suburban area. The urban district is a
54.76 km2major commercial center in Shanghai. The
average annual wage of employees was 40 527 RMB
Yuan in 2010. According to the Sixth National Census
at 0:00 hours on 1 November 2010, it had 1 085 130
residents with an average annual rate of increase of
0.19% compared with 1 064645 residents recorded at
the census 10 years earlier in 2000. The average annual
growth rate of the migrant population is 4.2%; 7.31%
of the total population was in 0–14 yr in 2010 which
was decreased by 3.43% than that in 2000 (http://tjj.xh.
sh.cn/forpart/rkpc_detail.aspx?newsid=2823&rootId=
35&rootType=dic&focus=115). The suburb district
is 371.57 square kilometers in Shanghai. It was
once mainly a rural area and is now undergoing
urbanization. The average yearly wage of employees
was 25 885 RMB Yuan in 2010. According to the
Sixth National Census at 0:00 hours on 1 November
2010, the suburb district had 2 429372 residents
with an average annual rate of increase of 7.15%
compared with 1 217 309 people at 2000 census.
The average annual growth rate of the migrant
population was 11.31%; 9.43% of the total population
was between 0–14 yr in 2010 which is a decline of
2.15% from that in 2000 (http://tj.shmh.gov.cn/mhtj/
ZLSJ/Tjgb/6751.htm). Before starting the survey, a
formal invitation letter was sent to each school in
the two selected districts and then a telephone call
was made to discuss and confirm adherence to the
data collection plan. In total, 15 elementary schools
(25.9% of the total) and 18 secondary schools (66.7%
of the total) in the urban district, 32 elementary
schools (76.2% of the total) and 36 secondary schools
(82.1% of the total) in the suburban district agreed to
participate and were included in the study. All school
children from 1st grade through 12th grade were
examined. In total, 70 822 students [urban area: 30 236;
suburban area: 40 856; male: 36 190 (51.1%); female:
34 632 (48.9%); aged 6–18 yr] were enrolled at the
study schools from March to July 2003 (first survey).
Of the 30 236 children enrolled at urban schools,
30 121 took part in the study, giving a response rate
of 99.62%. In addition, of the 40 586 children enrolled
at suburban schools, 40 310 took part in the study,
giving a response rate of 99.32%. One hundred fifteen
of the students from urban area (0.38%) and 276 from
suburban area (0.68%) were excluded due to sickness
or absence during the study. In 2008, we examined the
same schools again from March to July 2008 (second
survey). A total of 86 985 students were examined
[urban area: 29 367; suburban area: 56618; male:
44 368 (51.6%); female: 41617 (48.4%), aged 6–18 yr].
Of the 29 367 children enrolled at the urban schools,
29 230 took part, giving a response rate of 99.53%. Of
the 56 618 children enrolled at the suburban school,
56 375 took part, giving a response rate of 99.57%. One
hundred thirty-seven of the students from the urban
area (0.47%) and 243 from the suburban area (0.43%)
were excluded due to sickness or absence during the
time of Second survey.
The study had been approved by the Faculty
Hospital Ethics Committee of the Children’s Hospital
of Fudan University, Shanghai, China.
Measurements and quality control
All staff members involved in the two surveys
were trained under the same protocol for student
recruitment and height and body weight measurements.
Data on subjects’ weight, height, age, and gender were
Pediatric Diabetes 2012: 13: 572– 577 573
Zhang et al.
collected. All of the students were examined in school
clinics in the morning before breakfast. Height was
measured with the child standing straight in stockinged
feet using a fixed stadiometer. Body weight with shoes
and excess clothing removed was measured by standing
on an electronic scale which was calibrated daily with
standard weights. Heights were measured to the nearest
0.1 cm, weights was measured to the nearest 0.1 kg.
Definition of overweight and obesity
BMI was calculated as weight in kilograms divided by
the square of height in meters. Children were diagnosed
as normal, obese, and overweight according to the
centile curves from the International Obesity Task
Force (IOTF) (3). IOTF curves provide age- and sex-
specific cutoff points for children aged 2– 18 yr. BMI
of children 2–18 yr old was compared to IOTF curves.
For adolescents older than 18 yr, BMI values of 25
and 30 kg/m2were defined as overweight and obesity,
respectively. Individual BMI was compared to the age-
and sex-specific cutoff points, and the resulting status
(normal, overweight, or obese) was recorded.
Statistical analysis
Data were analyzed using stata statistical software
(version 6.0). The crude prevalence of obesity and
overweight was calculated and was then standardized
using local population data. The standardized
prevalence was calculated as the equation: P=
NiPi/N. Pwas the standardized prevalence, Pi was
the crude prevalence of each subgroup, Ni was the
reference people number of standard population from
each subgroup, and N was the total people number of
standard reference population. Chi-squared test was
used to compare prevalence of obesity or overweight
between the two surveys. Demographic data of the
investigated district were obtained from the statistical
yearbook from the Shanghai Statistics Bureau. The
statistical significance level was set at 0.05.
Results
The standardized prevalence of obesity increased
significantly from 3.35% in 2003 to 3.94% in 2008 (p <
0.01), and the standardized prevalence of overweight
increased significantly from 12.75 to 14.21% (p <0.01)
(Fig. 1, Table 1) in the same period. Additionally,
a significantly higher prevalence of overweight and
obesity was observed in the urban area when compared
to the suburban area (Table 1). The prevalence of
obesity decreased with age both in boys and girls, and
the prevalence of overweight increased during young
age with a peak at age 9–12 yr. Subsequently, a gradual
decrease with age was observed. The pattern in girls
was similar to that found in boys (Fig. 2). Interestingly,
the prevalence of obesity and overweight in boys was
significantly higher than that in girls both in the urban
and suburb area (p <0.01) (Fig. 1, Table 2).
Discussion
Our cross-sectional data suggest that the overall
prevalence of obesity and overweight in children
and adolescents had increased significantly during the
period 2003–2008 in the Shanghai area. This finding is
in contrast to reports from Sweden (6) and Australia
(7). In these countries, no increase of the prevalence of
childhood obesity was found in recent years. In fact,
decreasing prevalence of childhood obesity has been
observed in recent years in France (10) and Greece
(11). In addition, a cross-sectional study from Germany
showed a significant downward trend in the prevalence
of obesity rates between 2004 and 2008 in young
children while obesity rates in adolescents still increased
(8). This finding indicates that the trends of childhood
obesity prevalence differ among age groups. During
Fig. 1. The obesity and overweight prevalence aged distribution profiles in both genders.
574 Pediatric Diabetes 2012: 13: 572– 577
Obesity Shanghai trend in Chinese children
Table 1. The prevalence of overweight and obesity in children in suburban and urban groups between 2003 and 2008
Crude prevalence
of obesity (%)
Crude prevalence of
overweight (%)
Standardized prevalence
of obesity (%)
Standardized prevalence
of overweight (%)
Group 2003 2008 p* 2003 2008 p* 2003 2008 p* 2003 2008 p*
Urban Boy 7.23 7.88 0.03 20.45 21.41 0.04 6.53 7.19 <0.01 19.10 20.37 <0.01
Girl 2.66 2.82 0.41 12.33 13.51 <0.01 2.33 2.51 <0.01 11.38 12.37 <0.01
Sub-total 5.01 5.42 0.03 16.49 17.56 <0.01 4.47 4.90 <0.01 15.33 16.43 <0.01
Suburban Boy 3.88 5.93 <0.01 14.52 17.48 <0.01 3.55 5.01 <0.01 13.66 16.15 <0.01
Girl 1.59 2.23 <0.01 8.497 10.9 <0.01 1.45 1.80 <0.01 7.75 9.53 <0.01
Sub-total 2.76† 4.14† <0.01 11.57† 14.3† <0.01 2.51† 3.45† <0.01 10.73† 12.92† <0.01
Overall Boy 5.32 6.59 <0.01 17.06 18.82 <0.01 4.83 5.75 <0.01 16.05 17.71 <0.01
Girl 2.05 2.43 <0.01 10.13 11.79 <0.01 1.83 2.04 <0.01 9.34 10.56 <0.01
Total 3.72 4.58 <0.01 13.67 15.41 <0.01 3.35 3.94 <0.01 12.75 14.21 <0.01
*p-Values were the results from the statistical comparison of the prevalence between the year 2003 and 2008.
†p-Values were the results from the statistical comparison of the sub-total prevalence between urban and suburb area both
in the year 2003 and 2008, respectively, the p-values are all less than 0.05, data not shown in the table.
Fig. 2. The obesity and overweight prevalence in Shanghai children and adolescents aged 6 – 18 yr old.
the last 10 yr, the previously increasing prevalence
of childhood obesity had prompted governments in
many industrialized countries to initiate health care
intervention programs to combat childhood obesity.
These interventions, aimed at preventing childhood
obesity, might be responsible for the decrease of
childhood obesity in these countries.
Our data show that changes in the prevalence of over-
weight and obesity in China is age specific. The highest
prevalence of obesity was observed in the group of
6-yr olds (the youngest age group in our cohort). The
prevalence then decreased with age in both genders.
The highest prevalence of overweight occurred at age
9–12 yr both in boys and girls. Our results are in accor-
dance with the report by Nakano et al. in which the
prevalence of overweight peaked at 10–11 yr of age in
boys, and at 8–9 yr of age in girls (12). However, these
results differ from other observations whereupon the
prevalence of overweight and obesity increased contin-
uously with age (13, 14). The underlying cause of these
age and gender-specific patterns is largely unknown.
In our cohorts in Shanghai, both the prevalence and
the standardized prevalence of overweight and obesity
were higher in boys than in girls. The prevalence
of overweight in boys was nearly three times higher
than in girls in the urban area and nearly two times
higher in the suburban area. Rebelo et al. also reported
that between 1974 and 1997, the increasing rate of
overweight in boys (2.9–13.1%) was 1.6 times higher
than in girls (5.3–14.8%) in the Brazilian population
(15). This phenomenon, however, was not observed
in other countries: no significant differences between
genders have been found in the USA (13), Jordan (16)
and Hungary (17). Sweeting and colleagues reviewed
English language publications from 1996 to 2007 and
found no significant gender differences in relation to
obesity prevalence in most reports (18). In our study,
the higher prevalence observed in boys might be due
to the one-child policy which is specific for China and
the traditional Chinese values favoring boys in the
family (19).
In addition, we found that the increase of obesity
and overweight prevalence was significantly higher in
the suburban area than that in the urban area. This
is in agreement with studies in other populations: for
example, in Brazil, the annual increase of overweight
Pediatric Diabetes 2012: 13: 572– 577 575
Zhang et al.
Table 2. The prevalence of obesity and overweight in children and adolescents aged 6– 18 yr in Shanghai between genders
Number Obesity
Crude
prevalence of
obesity (%)
Standardized
prevalence of
obesity (%) Overweight
Crude
prevalence of
overweight (%)
Standardized
prevalence of
overweight (%)
Group Boy Girl Boy Girl Boy Girl Boy Girl Boy Girl Boy Girl Boy Girl
2003 Urban 15 444 14 677 1117 391 7.23 2.66* 6.53 2.33† 3158 1809 20.45 12.33* 19.1 11.38†
Suburban 20 538 19 772 797 315 3.88 1.59* 3.55 1.45† 2982 1680 14.52 8.50* 13.66 7.75†
Total 35 982 34 449 1914 706 5.32 2.05* 4.83 1.83† 6140 3489 17.06 10.13* 16.05 9.34†
2008 Urban 14 987 14 243 1181 402 7.88 2.82* 7.19 2.51† 3209 1924 21.41 13.51* 20.37 12.37†
Suburban 29 161 27 214 1728 606 5.93 2.23* 5.01 1.80† 5098 2965 17.48 10.90* 16.15 9.53†
Total 44 148 41 457 2909 1008 6.59 2.43* 5.75 2.04† 8307 4889 18.82 11.79* 17.71 10.56†
*p-Values were the results from the statistical comparison of the crude prevalence between the two genders both in the year
2003 and 2008, respectively, the p-values are all less than 0.05, data not shown in the table.
†p-Values were the results from the statistical comparison of the standardized prevalence between the two genders both in
the year 2003 and 2008, respectively, the p-values are all less than 0.05, data not shown in the table.
prevalence in urban areas (4.9–18.4%) was more
than double than that in rural areas (3.1–8.4%) (20).
Oulamara et al. reported a remarkable increase of
overweight prevalence in urban children compared
with that of children from rural areas (21). However,
our finding differs from a previous study in Chinese
children in which Wang et al. reported a slight
increase of obesity prevalence in rural areas (5.9–6.4%)
compared to urban areas (7.7–12.4%) in the early
2000s (20). These differences amongst populations
from different areas could be attributed to differences
in socioeconomic conditions as well as to differences in
life style.
During the study period between 2003 and 2008,
the number of urban children studied fell from 30 236
to 29 367, while the number of suburban children rose
from 40 856 to 56 618. Unlike in Western countries, the
majority of the Chinese native permanent citizens live
in urban areas. There is little motivation to migrate
to suburban regions since schools and health care
facilities usually are considered better in the urban
areas. Although it was not possible to get detailed
information on residence for each student in this study,
considering the annual average rate of increase of resi-
dents was only 0.19%, while the average annual growth
rate of the migrant population was 4.2% between the
year 2010 and 2000, and the total population in 0–14
yr in 2010 decreased by 3.43% during the same period
(http://tjj.xh.sh.cn/forpart/rkpc_detail.aspx?newsid=
2823&rootId=35&rootType=dic&focus=115), it can
be deduced that the migrant population consisted
mainly of adults searching for new working positions
or business opportunities. The decline of student
numbers in the urban area may be mainly due to
declining birth rates in inner cities. On the basis of the
principle of proximity of local school admission, the
majority of the students are nearby native residents
and the change in student numbers is highly if not
exclusively related to changing birth rates. The number
of births per year in Shanghai has decreased since
1987. The fall in the number of the native student
population in urban Shanghai is in accordance with
this phenomenon (22). With the rapid economic
improvement in Shanghai, a large number of compa-
nies were established during the last decades in the
suburban areas. This change is followed by an influx
of workers and families into such suburban areas (23).
The high average annual growth rate of the migrant
population (11.31%) and the somewhat lower annual
average rate of increase of suburban residents (7.15%)
were in accord with the above report (23) (http://
tj.shmh.gov.cn/mhtj/ZLSJ/Tjgb/6751.htm). The rapid
increase in the migrant population may have con-
tributed to the increased student population in the
second round survey. One study analyzed the origin
of this population and suggested that most of it came
from small to medium sized cities or rural counties
(24). Ji and colleagues compared children’s BMI
profiles in different areas, and found that children’s
BMI in small to medium cities or rural counties were
lower than those found in large cities, such as in
Shanghai (25). We conclude therefore that the change
of obesity prevalence in the urban area most likely
reflects a real trend in the study period within the
given population, while the obesity prevalence in the
suburban area may be underestimated due to the rapid
increase in the migrant population.
In conclusion, in our study using data from two sets
of large, consecutive cross-sectional, and representative
cohorts, we observed that the prevalence of obesity and
overweight in children and adolescents in Shanghai
increased significantly between 2003 and 2008. This
finding suggests that the prevalence of obesity in
children is still increasing in China. This is in contrast
to reports from several developed countries and
might reflect the different socioeconomic conditions
and changes thereof in the two types of societies.
Intervention programs seem to be warranted to reduce
the ever increasing prevalence of obesity at young age
in China.
576 Pediatric Diabetes 2012: 13: 572– 577
Obesity Shanghai trend in Chinese children
Acknowledgements
We would like to thank all the students, teachers, and staff of
the Centers for Disease Control and Prevention in the Minhang
and Xuhui Districts, Shanghai, for their invaluable support and
dedication to the project. Prof. Na He, from the Department
of Epidemiology of Fudan University, helped to analyze the
data. We thank American Journal Experts (AJE) for editing
this manuscript and giving support in manuscript writing. This
study was supported by a grant from Shanghai Science and
Technology Commission (024119013 and 064119514). W. K. is
supported by the LIFE program and the IFB adiposity diseases
of the Medical Faculty of the University of Leipzig, Germany.
There exists no conflict of interest.
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