Vol.5, No.1, 24-29 (2013) Health
Overweight, obesity and associated factors among
secondary school students in a northern city of
Vietnam in 2011*
Huong Thi Le1#, Nga Thi Thu Vu1#, Doan Thi Thu Huyen1, Nguyen Van Toan2
1Institute for Preventive medicine and Public Health, Hanoi Medical University, Hanoi, Vietnam;
#Corresponding Author: hathuhuong@yahoo.com, vuthunga@hmu.edu.vn
2Bac Giang Secondary School of Nursing No1, Hanoi, Vietnam; doanthuhuyen@hmu.edu.vn
Received 30 August 2012; revised 30 September 2012; accepted 6 October 2013
Overweight and obesity is an emerging public
health problem among school-aged children in
Bac Giang city in the Northen part of Vietnam
recently. This study aims to identify overw eight-
obesity prevalence of se condary school childre n
in this city and it’s associated factors. The study
was a nested case control in a cross-sectional
study design in 1528 secondary students se-
lected from 4 secondary schools in 2 inner
communes and 2 suburban communes of Bac
Giang city, Vietnam. Result: Overweight preva-
lence among secondary school students in Bac
Giang was 6.7%, the prevalence of obesity was
2.0%. Overweight and obesity is more preva-
lence in male students, inner communes and
students from family have higher income and
higher food expense. Overweight and obesity
was associated with higher energy intake, more
fat consumption, having supplement meals and
bedtime-meal, increased physical activities and
increased sleep duration. Conclusion: Educa-
tion campaign targeting reducing overweight and
obesity should target both parents about dietary
adequacy and balance and children about more
physical activities.
Keyw ords: Overweight; Obesity; Secondary
Students; Vietnam
Overweight and obesity are defined as abnormal or
excessive fat accumulation that may impair health and
becoming a trendy public health problem worldwide
[1-6]. In Vietnam, thanks to the improvement of socio-
economic status in recent years, there has been a chang-
ing of eating habit from a cereal based diets to diets with
more meat, fish, dairy products, sugar, soft drinks, con-
fectionary and processed food. Concurrently, emerging
increase of overweight and obesity is occurring across
the country among children and adolescent, especially in
big cities. Studies in Vietnam have shown that over-
weight and obesity prevalence has been steadily upward
across the country during the past decade. In the biggest
city of Vietnam, the number of people overweight and
obesity doubled from 21.4% and 36.8% during 3 years
from 2002 to 2005. The number of obesity boys also
increased three times from 6.9% in 2002 to 22.5% in
2005 [7-14]. Studies in Vietnam and elsewhere also
found out that diets with high energy, more fat and pro-
tein, high level of sweet, confectionary, soft drinks con-
sumption with low physical activities and spen ding more
time for watching TV and playing games on computers
were associated with obesity and overweight [10,11,
15-19]. In Bac Giang city in the Northern part of Viet-
nam, as according to the City Health Department, over-
weight and obesity has been increasing in recent years.
However, full understanding of the prevalence and its
associated factors are unknown; hence, scientific-based
evidence for intervention formulation is absence. There-
fore, we conduct this study in order to:
1) Identify the prevalence of overweight and obesity
among secondary students in Bac Giang city of Vietnam
in 2011.
2) Describe associated factors of overweight and obe-
sity in secondary students in Bac Giang in 2011.
*All the authors of this article declare that there is no competing o
interest regarding the publication of this article.
HT Le, NTT Vu and TTH Doan were responsible for all aspects o
rotocol development, study coordination, data collection, data analysis
and report writing.
2.1. Study Location
Bac Giang city, located 60 kilometers far from Hanoi
Copyright © 2013 SciRes. OPEN A CCESS
H. T. Le et al. / Health 5 (2013) 24-29 25
in the north. This is the provincial city and the socio-
economic and administrative hub of Bac Giang province.
The city has over 102 thousand people; live in 7 inner
communes and 9 suburban communes. Each commune
has one primary school, one secondary school and all
children of relevant age, who have permanent living
status at this commune, are all enrolled in these schools.
2.2. Study Population
The study population is secondary students enrolled in
grade 6 to grade 9 with age ranging from 11 years old
(grade 6) to 14 years old (grade 9) and a few with older
age from total 16 secondary schools across the city.
2.3. Time of Study
From January to September of 2011.
2.4. Design
2.4.1. Study Design
This is a nested case control study in a cross sectional
study. The first phase is a cross-sectional study when all
study subjects were measured height and weight to iden-
tify the point prevalence of overweight and obesity. In
the second phase, all subjects who were identified as
overweight or obesity were paired with other none-cases
subjects in the study to explore the associated factors of
overweight and obesity.
2.4.2. Sample Size and Sampling Method
Phase 1: Multi-stage cluster was applied to recruit
study’s subjects. First, the list of 7 secondary schools in
the inner communes and the list of other 9 schools in the
suburban communes in Bac Giang city were collected
from the City’s Department of education. Next, 2 schools
in the inner communes and 2 schools in the suburban
communes were randomly selected fro m these lists. Then,
in each school, each grade is regarded as a cluster and 3
classes from each cluster were randomly selected into the
study. All students in these classes were recruited into
study and were measured their height and weight.
The calculation of sample size for this phase based on
the prevalence of overweight, obesity of 8.3% from a
recent study in an area in Vietnam that has similar socio-
economic status as compared to Bac Giang city [11],
with the level of confidence at 95%, margin of error at
0.02% and design effect is 2. Minimum sample size
needed is 1462 students; however, in fact, 1528 students
were recruited into the study.
Phase 2: All overweight, obesity students detected in
the first phase will be recruited as cases and were paired
with one control. The controls were students with the
same age, gender and study at the same schools of cases
and have normal BMI for age. Controls were selected
from study subjects. Subjects in the phase 2 will be in-
terviewed about their demographic information, eating
habit, 24 h dietary, frequency of food consumption dur-
ing the last week, physical activities and static activities.
Parents or direct caregivers of these students were inter-
viewed about their family’s socio-economic status.
2.4.3. Dat a Collection
Student’s height was measured by Microtoise height
meter with the precision of 0, 1 centimeter. The meter
was tested and placed in a stable location and adjusted to
0 value before each measument; students were asked to
take out shoes and hat and were instructed to stand
straightly in the meter. Height was recorded as meter
with one decimal digit. Weight was measured by elec-
tronic SECA weigh ter with the precision of 0, 1 k ilogr am.
The weighter was tested and placed in a stable location;
students were asked to take out all of their shoes and
coats and were instructed to straightly stand in the mid-
dle of weighter. Weight was recorded as kilogram with
one decimal digit. Demographic, eating behaviors and
other information of students were collected by a pre-
designed, piloted questionnaire via face-to-face inter-
views. Questions regarding eating habit, 24 h-dietary and
frequency of food consumption in the last week were
adapted from conventional questions which are used
widely in other studies in Vietnam. Socio-economic sta tus
of students’ family was gathered via telephone-based
interviews with their parents.
Anthrometric measurement and interviews were per-
formed by experienced interviewers from Hanoi Medical
University. Before fieldwork, all interviewers were well
trained about the standard operation procedures to meas-
ure weight, height and administer interviews.
All children and their parents were carefully explained
about the purpose of the study and orally accepted to
participated to the study befo re data collection.
2.4.4. Dat a Analysis
Obesity and overweight identification. Overweight
and obesity was determined using body mass index per
age per gender (BMI) (a measure of weight adjusted for
height, calculated as weight in kilogram divided by the
square of height in meter (kg/m2) and WHO Reference
2007 for 5 - 19 years to monitor the growth of school-age
children and adolescents [20].
Overweight:+1SDBMI per age2SD
Obesity:2SDBMI per age3SD
Nutrition need and diets balance asses smen t and
analysis were calculated based on the Recommended
Nutrition Need for Vietnamese, published by Vietnam
National Institute of Nutrition [21]. Converting from
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H. T. Le et al. / Health 5 (2013) 24-29
Copyright © 2013 SciRes. OPEN A CCESS
food intake into energy intake was performed based on
the Vietnam table of food’ nutritious components [22].
The data then was cleaned before entering into EPI-
DATA software version 2.0. We used Stata software ver-
sion 11 to analyze the data. Descriptive statistic was per-
2 tests were done to test the differences of pro-
portions of obesity and overweight among different age
groups and gender. Logistic regression was performed to
examine the relation between overweight, obesity and
associated factors. All independent variables were first
tested with univariate analysis. All important independ-
ent variables with P < 0.2 in the univariate analysis were
put into multivariate logistic regression model. Multi-
variate logistic model was refitted, tested until the final
model with the best fit was achieved.
3.1. Study’s Subjects Description
The response rate of participants in the study was
100% for both students and their parents. There were
1528 students, of whom 763 male students (49.9%) and
765 female students (51.1%) participated in the study.
There was equal gender distribution across age groups.
Students at 12 years old age-group took the highest per-
cent of the total sample size (27.6%) and 46.7% partici-
pated students were from schools situated in the inner
communes of Bac Giang.
3.2. Overweight and Obesity Prevalence
In general, the proportion of overweight and obesity
were 6.7% and 2.0% respectively. There was no signifi-
cant difference of overweight and obesity across age
groups. However, there was significant difference of over-
weight and obesity rate by gender. Both overweight and
obesity rate in male students were more than 2 times
significantly higher than the similar rates in female stu-
dents. Students in inner communes had significantly h ig he r
proportion of overweight and obesity than those live in
suburban communes (Table 1).
Overweight and obesity students had average family
income significantly higher than students with normal
weight do (799.2 ± 130.1 VND vs 688.6 ± 150.0 VND,
respectively). Moreover, families of students with over-
weight and obesity spent significantly more money for
food than families of students with normal weight do
(1740.3 ± 452.3 VND vs 1573.9 ± 489.3, respectively)
(Table 2).
Diets analysis shows that both overweight and obesity
students and students with normal weight had diets with
total energy intake and energy from glucid and protid fall
within the normal range but both groups had energy in-
take from lipid exceed the normal range (24.4$ and
23.9% vs 18% - 20%). Students with overweight and
obesity had a significantly higher total energy intake than
students with normal weight (2342.6 ± 468.8 Kcal vs
2048.6 ± 344.2 Kcal, respectively) (Table 3).
Summary of logistic analysis is presented in Ta b l e 4.
Favor to eat sweet and fried food and eating practice
such as frequent eating confectionary, sweet and sweeten
milk were not associated with overweight and obesity.
Increased total energy intake, having supplement meals,
having bedtime-meal and eating fat for more than 3 times
a week were associated with being overweight and obe-
sity. In contrast, increased time for physical activities s uc h
as riding, walking, having exercise, ect. and increased
sleeping duration were protective associated factors.
The prevalence of overweight, obesity among 1528
students of 4 secondary schools in Bac giang (6.7%
overweight and 2.0% obesity) was lower than the result
Table 1. Distribution of overweight, obesity by age, gender and place of residence.
Distribution Overweight % (CI) Obesity % (CI)
Total (n = 1528) 6.7 (5.5 - 8.0) 2.0 (1.3 - 2.7)
By age group
11 years old 6.9 (4.0 - 9.6) 2.5 (0.7 - 4.2)
12 years old 7.8 (5.2 - 10.4) 1.2 (0.1 - 2.2)
13 years old 6.6 (4.0 - 9.2) 1.9 (0.5 - 3.3)
14 years old 5.7 (2.7 - 7.3) 2.4 (0.9 - 3.8)
By gender
Male 9.6 (7.5 - 11.7)*** 2.8 (1.6 - 3.9)*
Female 3.9 (2.5 - 5.3) 1.2 (0.4 - 1.9)
By place of residence
Inner communes 10.1 (7.9 - 12.3)*** 3.2 (1.9 - 4.4)***
Suburban communes 3.4 (2.1 - 4.7) 0.8 (0.2 - 1.4)
Differences between proportions were tested by Fisher Exact Test. ***P < 0.001; *P < 0.05
H. T. Le et al. / Health 5 (2013) 24-29 27
Table 2. Household economic status by overweight-obesity status.
Overweight, obesity studentsNormal weight students
Household economic status SD (M ± SD) P (T test)
Per capita average monthly food expense (million VND)799.2 ± 130.1 688.6 ± 150.0 P < 0.001
Per capita everage monthly income (million VND) 1740.3 ± 452.3 1573.9 ± 489.3 P = 0.02
Table 3. Characteristic of the diets.
Overweight and Obesity studentsNormal weight students
Diet characteristic (n = 88) (n = 88) Requirements of energy intake
Total energy intake (Kcal) 2342.6 ± 468.8*** 2048.6 ± 344.2 2100 - 2500
Energy intake from protein/Total energy intake (%) 16.6 18 12 - 14
Energy intake from lipid/Total energy intake (%) 24.4 23.9 18 - 20
Energy intake from glucid/Total energy intake (%) 59 57.9 66 - 70
Pr o t e i n f r o m a ni m a l / To t a l pr o t e i n (% ) 34. 9 30 30 - 50
Lipid from plant/Total lipid (%) 31.3 35.3 30 - 50
Differences of means were performed by T test; ***P < 0.001; **P < 0.01;*P < 0.05.
Table 4. Associated factors of overweight and obesity.
Univariate logistic Final multivariate logistic
Independent variables Crude OR (95% CI)P Adjusted OR (95% CI) P
Like eating sweet 1 (0.52 - 1.94) 1.000
Like eating fat 11.15 (1.40 - 89.12) 0.023
Like eating fried food 1.05 (0.58 - 1.89) 0.880
Like drinking soft drinks 1.73 (0.95 - 3.15) 0.071
Total energy intake by 100 calories increasement 1.21 (1.11 - 1.32) 0.000 1.23 (1.1 - 1.36) 0.000
Having supplement meals 1.97 (1.50 - 5.92) 0.002 3.87 (1.51 - 9.94) 0.005
Having snacks 2.09 (1.14 - 3.81) 0.016
Having bedtime-meal 2.11 (1.10 - 4.04) 0.025 2.43 (1.02 - 5.82) 0.046
Having fat more than 3 times/week 2.96 (1.39 - 6.30) 0.005 2.61 (1.01 - 6.78) 0.048
Having fried food more than 3 times/week 0.52 (0.30 - 0.95) 0.034
Having confectionary more than 3 times/week 0.91 (0.50 - 1.65) 0.760
Having soft drinks more than 3 times/week 1.27 (0.64 - 2.48) 0.490
Having sweeten milk more than 3 times/week 0.77 (0.41 - 1.45) 0.420
Total time for physical activities with 10 minutes increasement0.94 (0.90 - 0.99) 0.009 (0.91 - 0.85 - 0.97) 0.004
Total time for inphysical activities with 10 minute increasement
(watching TV, playing games, reading books, ect.) 1.053 (1.02 - 1.09) 0.006
Total time for sleeping (in hour) 0.42 (0.30 - 0.60) 0.000 0.32 (0.21 - 0.49) 0.000
of a similar study in Hue in 2007 [11] and lower than the
rate found in other recent studies in Hanoi, Buon Ma
Thuot and Ho Chi Minh city [9,12,15,17]. This lower
prevalence in Bac Giang could be explained by higher
socio-economic development and better nutrition mode
in Hanoi, Ho Chi Minh city and in other regions of Viet-
The prevalence of overweight, obesity was higher in
male students as compared with female students. This
finding is similar to the finding of Le Thi Hai et al. in
Hanoi in 2002, Vo Thi Dieu Hien et al. in Hue in 2007
and the findings of studies elsewhere in the region [9,11,
Our study shows higher prevalence of overweight and
obesity in the inn er communes compared to the suburb an
communes, suggesting possible differences of socio-eco-
nomic status, eating behaviors and physical activities.
Additionally, students with overweight and obesity had
families with higher per capita income and higher money
for food expense. This finding is similar to the finding of
other studies [11,25].
After controlled for other factors, higher energy intake
and more fat consumption were associated with over-
weight and obesity. Our result is similar to the result of
other studies in Vietnam and elsewhere [16-18,26]. Other
eating habit such as having supplement meals or bed-
time-meal were also found significantly associated with
overweight and obesity, suggesting that there is no need
for further supplement meal and bedtime-meal for chil-
dren participated in this study. In the multivariate logistic
model, increased time for physical activities (riding bi-
cycle, exercising and walking to schools) was also asso-
ciated with lower risk of overweight and obesity, similar
to the result of Vo Thi Dieu Hien, Duncan Scott, Hong,
Copyright © 2013 SciRes. OPEN A CCESS
H. T. Le et al. / Health 5 (2013) 24-29
T.K et al., Pitrou Isabella and Sirikulchayanonta Chutima
et al. [7,11,19,25-27]. Though it is still argued in litera-
ture about the relationship between sleep duration and
overweight and obesity, we found longer sleeping time
was associated with lower rate of overweight and obesity.
This result is similar to the result of Tran Thi Hong Loan,
Hoang Thi Minh Thu and Vo Thi Dieu Hien and studies
elsewhere outsi de Vietnam [11,17,18,23].
However, unlike findings of other studies in Vietnam
and elsewhere, frequent eating sweet, confectionary and
drinking soft drinks were not found associated with over-
weight and obesity [11,16,19], suggesting that overweigh t
and obesity in the study population in Bac Giang is more
related to dietary characteristic.
The prevalence of overweight, obesity among second-
dary school students in Bac Giang city of Vietnam in
2011 was 6.7% and 2.0% respectively, lower than similar
prevalence in other regions of Vietnam. The prevalence
was higher in male students and students from families
with higher income and higher food expense and associ-
ated with higher energy intake, more fat consumption,
having supplement meals and bedtime-meal, increased
time for physical activities and longer sleep duration.
Parents should be educated about dietary adequacy and
balance, limiting supplement meals and bedtime meal for
children and children should be educated about increase-
ing physical activities to reduce risk of being overweight
and obesity.
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