Background: The prevalence of overweight and obesity (OW/OB) has increased rapidly in Vietnam. This study aimed to elucidate the factors influencing OW/OB among secondary schoolchildren. Method: A survey was conducted in January 2014 in four randomly selected state schools in two Hanoi urban districts, and 821 students in grade six (11–12 years old) participated. Definitions of OW/OB followed the World Health Organization standard cut-offs. Results: Overall, 4.1% of children were underweight, 59.7% were normal weight, 17.1% were overweight, and 19.1% were obese. The odds of OW/OB were lowest among children whose parents had college/university degrees [father (aOR =0.65, 95% CI: 0.42–1.00); mother (aOR =0.63, 95% CI: 0.41–0.97)] compared with those whose parents had only a primary education. Children with an OW/OB family history had an increased risk of OW/OB. Other associated factors include parental OW/OB and birth weight (BW). The odds of OW/OB were highest among children with parents with OW/OB [father (aOR =2.022, 95% CI: 1.34–3.04); mother (aOR =2.83, 95% CI: 1.51–5.30)] compared with those with normal-weight parents. Children with both parents having OW/OB [both parents (aOR =6.59, 95% CI: 1.28–33.87) had the highest risk, followed by one parent (aOR =2.22, 95% CI: 1.50–3.27)] and then neither parent having OW/OB. Moreover, high-birth-weight children [BW ≥ 3500 g (aOR =1.52, 95% CI: 1.07–2.15)] had greater odds than did normal-birth-weight children. Children who slept 11 h per day [8–11 h (aOR =0.57, 95% CI: 0.40–0.81) or more (aOR =0.44, 95% CI: 0.22–0.87)] had lower OW/OB odds than those who slept 8 h or less. Children with specific positive lifestyle behaviours had lower risk of OW/OB than those who did not engage in positive lifestyle behaviours. The odds were lower among children who exercised for weight reduction (OR = 0.16, 95% CI: 0.11–0.23), lowered food intake (aOR = 0.12, 95% CI: 0.09–0.17), and added vegetables to their diet (aOR = 0.26, 95% CI: 0.19–0.35). Conclusion: The results suggest that parents and children with OW/OB parents or a high BW should be educated to prevent OW/OB at an early stage. Positive lifestyle behaviours should be adopted by the students.
Keywords: Overweight; Obesity; Children; Prevalence; Vietnam
Overweight and obesity (OW/OB) are global epidemics. A report from the WHO indicated that in 2016 more than 18% of children and adolescents aged 5–19 were overweight or obese worldwide [[
A cross-sectional survey was conducted in January 2014. Using a stratified sampling method, two districts were randomly selected from four urban districts in Hanoi, and then four state junior high schools were randomly selected from those two urban districts. In each school, five classes of grade six (11–12 years) were randomly selected, and all the students and their parent(s) in the selected classes were invited to participate in the study. The parents and students were required to provide written consent to participate in the study.
Each consent form required the signatures of the student and their parent(s) to enable participation; to participate, both the student and his/her parent must sign the consent form.
Students were given a self-administered questionnaire investigating their physical activity and nutrition (detail of the questionnaires in Additional file 1). They completed the questionnaires while sitting in their own classrooms and had 30 min to answer all the questions. Beforehand, public health professionals explained the details of the questionnaire and the purpose of the survey to the students.
Health examination and anthropometric measurements: Two groups, each including two doctors and three nutritionists, measured the weight of each student using BS-150WT digital weighing scales (Dretec, Koshigaya, Japan), which are precise to within 100 g [[
Body mass index (BMI)-for-age was calculated using the formula m/h
Information on parental anthropometric measurements, family history, and environmental factors was collected by distributing questionnaires to the students' parent(s) (see Additional file 2). Because each student who participated in the study was weighed using BS-150WT digital weighing scales (Dretec), the same weighing scales were also used to measure the parents' weights. To ensure the same tool measured weight and to benefit the participants of the study, all students were provided a BS-150WT digital scale. The research group provided instructions on adhesive-backed papers to instruct parents about the correct way to measure their height. The data were then recorded in the questionnaires by the students' parent(s). Parents who had a BMI ≧25 kg/m
Laboratory tests were conducted in the Biochemistry Department of Bach Mai Hospital, Hanoi, Vietnam according to the ISO 15189 standard.
Students were instructed to skip breakfast on the day of the examination and had to fast for at least 10 h. The adequacy of the fasting period was confirmed before blood samples were collected. Venous blood (5 ml/student) was collected between 7:30–10:00 AM by nurses who were working in the Pediatric Department of Bach Mai Hospital in 1 g/L tubes containing ethylenediaminetetraacetic acid as an anticoagulant, and the samples were placed on dry ice. The samples were then transported from the study site to the Biochemistry Department of Bach Mai Hospital. They were centrifuged at 5000 rpm for 10 min. Plasma glucose was determined using the glucose hexokinase method with a Cobas® 8000 (c702) chemistry analyser (Roche, Basel, Switzerland). HbA1C was measured using the boronate affinity high-performance liquid chromatography method with an Ultra
Data analysis was performed using SPSS statistics desktop version 21.0 media pack software (IBM, Armonk, NY, USA). We used a simple chi-square test at the α = 0.05 level of significance to test the associations of different risk factors. Variables showing significant associations with OW/OB in children were further identified using a logistic regression test to determine the odds ratio (OR) and the 95% CI. The risk factors for OW/OB were adjusted for sex, and multiple logistic regression analysis was used to determine the adjusted odds ratio (aOR) of each risk factor. In the analysis, there were two outcome variables: the OW/OB variable included the combined data of overweight and obesity, and the other variable incorporated the remaining data, which were not related to OW/OB in children, as a reference.
The study protocol was approved by the Ethics Committee of Bach Mai Hospital, Hanoi, Vietnam with the decision letter Number 529 QD-BM on the 10th of May 2013 and the Ethics Committee of the National Center for Global Health and Medicine, Japan, with the number 1496 on the 1st of October 2013. Before the collection of questionnaire data and venous blood samples, information sheets and consent forms were distributed to parents and students by the schools. Students participating in the study agreed to provide written informed consent with written approval from their parent(s). All participants could withdraw from the study at any time without any threats or disadvantages.
From four districts in central Hanoi, two districts containing a total of 29 state schools were selected. Four randomly selected schools agreed to participate in the study. Information sheets and consent forms were distributed to 936 students and their parents. After both the student and his/her parent signed the consent form, 821 students participated in the study. Table 1 shows the characteristics of the students. The proportions of the students in each BMI range were evaluated according to the WHO standards. The proportion of underweight children was the lowest (3.9% of boys and 4.3% of girls). The proportions of boys (18.9%) and girls (15.4%) who were overweight did not differ significantly, χ
Prevalence for boys and girls
Proportions of boys and girls in each morphological category (based on BMI measurements) Underweight % (n) Normal % (n) Overweight % (n) Obesity % (n) Total (n) Boys ( 3.9% (15) 44.7% (170) 18.9% (72) 32.4% (123) 380 Girls ( 4.3% (19) 72.6% (320) 15.4% (68) 7.7% (34) 441 Total 4.1% (34) 59.7% (490) 17.1% (140) 19.1% (157) 821
P < 0.001; chi square = 91.555 Boys/girls presenting overweight or obesity: OR: 3.503 (95% CI: 2.60–4.73)
When comparing the measurements of BMI and waist circumference, it is apparent that there was a large gender difference in waist circumference (boys: 71.01 ± 9.60 cm, girls: 66.13 ± 7.62 cm, p = 0.001) as well as in BMI (boys: 19.9 ± 3.6 kg/m
As shown in Table 2, the biochemical data for total cholesterol and low-density lipoprotein also showed significant differences between boys and girls (total cholesterol: boys 4.33 ± 0.78 mmol/L, girls 4.20 ± 0.72 mmol/L, p = 0.012; LDL boys 2.37 ± 0.71 mmol/L, girls 2.20 ± 0.66, p = 0.001 mmol/L). Considering the family and children characteristics shown in Table 3, the odds of OW/OB were lowest among children whose parents had college / university degrees [father (aOR =0.65, 95% CI: 0.42–1.00); mother (aOR =0.63, 95% CI: 0.41–0.97)] compared with those whose parents had only a primary education. Children with an OW/OB family history had an increased risk of OW/OB. The odds were highest among children with parents with OW/OB [father (aOR =2.022, 95% CI: 1.34–3.04); mother (aOR =2.83, 95% CI: 1.51–5.30)] compared with children whose parents had a normal weight. The associated factors included parental OW/OB, and the risk was the highest among children with both parents having overweight or obesity [both parents (aOR =6.59, 95% CI: 1.28–33.87); one parent (aOR =2.22, 95% CI: 1.50–3.27)] compared with those with neither parent having overweight or obesity. Regarding birth weight (BW), the odds were greatest for high-birth-weight children [children with a BW 3500 g or greater (aOR =1.52, 95% CI: 1.07–2.15)] compared with those with a normal BW.
Anthropometric and laboratory data for boys and girls
Factor Sex Mean ± SD BMI (kg/m2) boys 380 19.90 ± 3.60 0.001 girls 441 18.44 ± 2.68 Arm circumference (cm) boys 376 23.51 ± 3.19 0.001 girls 431 22.40 ± 2.32 Hip circumference (cm) boys 379 81.67 ± 7.89 girls 440 80.99 ± 6.83 0.192 Waist circumference (cm) boys 379 71.01 ± 9.60 0.001 girls 440 66.13 ± 7.62 Diastolic blood pressure (mmHg) boys 379 70.48 ± 10 girls 440 70.72 ± 8.6 0.567 Systolic blood pressure (mmHg) boys 379 111.09 ± 10.3 girls 440 108.89 ± 12.4 0.170 Glucose (mmol/L) boys 380 4.85 ± 0.52 0.048 girls 441 4.78 ± 0.53 T_cholesterol (mmol/L) boys 380 4.33 ± 0.78 0.012 girls 441 4.20 ± 0.72 Triglyceride (mmol/L) boys 380 1.05 ± 0.60 0.132 girls 441 1.11 ± 0.54 HDL_C (mmol/L) boys 380 1.50 ± 0.39 0.907 girls 441 1.49 ± 0.40 LDL_C (mmol/L) boys 380 2.37 ± 0.71 0.001 girls 441 2.20 ± 0.66 HbA1c (%) boys 380 5.44 ± 0.26 0.362 girls 441 5.42 ± 0.24
Factors associated with overweight or obesity among children aged 11–12 years, Hanoi, Vietnam
Factor OR 95% CI aOR 95% CI Lower Upper Lower Upper FAMILY CHARACTERISTICS Father's education Primary school 1 1 Secondary school 0.80 0.15 4.23 0.801 0.72 0.12 4.32 0.715 College or university 0.73 0.48 1.09 0.122 0.65 0.42 1.00 0.050 Mother's education Primary school 1 1 Secondary school 1.62 0.46 5.68 0.448 1.14 0.30 4.31 0.842 College or university 0.69 0.46 1.04 0.079 0.63 0.41 0.97 0.037 Father's BMI 18.5–24.9 1 1 < 18.5 0.66 0.29 1.45 0.317 0.62 0.26 1.44 0.265 ≥ 25 1.92 1.30 2.84 0.001 2.02 1.34 3.04 < 0.001 Mother's BMI 18.5–24.9 1 1 < 18.5 0.68 0.28 1.63 0.368 0.69 0.28 1.72 0.428 ≥ 25 2.28 1.26 4.13 0.007 2.83 1.51 5.30 0.001 Parental overweight or obesity (classified by BMI) Neither parent overweight or obese 1 1 One parent overweight or obese 1.94 1.35 2.80 0.001 2.22 1.50 3.27 < 0.001 Both parents overweight or obese 7.18 1.50 34.89 0.015 6.59 1.28 33.87 0.024 CHILD CHARACTERISTICS Number of siblings in the family 1 1 1 2 1.27 0.79 2.04 0.323 1.29 0.79 2.11 0.305 ≥ 3 0.66 0.33 1.26 0.202 0.87 0.43 1.75 0.697 Birth order among siblings 1 1 1 2 0.89 0.66 1.19 0.420 0.80 0.58 1.09 0.149 ≥ 3 0.40 0.16 1.00 0.050 0.47 0.18 1.22 0.122 Breastfeeding history (none as reference) Breastfed by mother for at least 6 months after birth 0.80 0.58 1.12 0.191 0.87 0.62 1.22 0.410 Birth weight (grams) 2500–3500 1 1 < 2500 0.40 0.18 0.87 0.021 0.51 0.22 1.14 0.101 ≥ 3500 1.60 1.14 2.23 0.006 1.52 1.07 2.15 0.019 Time spent watching television (hours per day) < 2 1 1 2–4 0.97 0.67 1.41 0.862 1.00 0.68 1.49 0.989 > 4 1.56 0.89 2.72 0.122 1.78 0.99 3.20 0.056 Sleep per day (hours) < 8 1 1.00 8–11 0.64 0.46 0.90 0.009 0.57 0.40 0.81 < 0.001 > 11 0.47 0.24 0.90 0.022 0.44 0.22 0.87 0.018 PHYSICAL ACTIVITY AND LIFESTYLE BEHAVIOURS OF CHILDREN Exercised in last 7 days (0–2 days/week as reference compared with those who did 3 days or more per week) Exercised for 60 min per day 1.19 0.87 1.63 0.276 0.96 0.69 1.34 0.83 Intense exercise for 20 min per day evidenced by sweating and breathing hard 1.15 0.82 1.62 0.411 0.97 0.68 1.37 0.84 Participation in sports in the last 12 months (None as reference) 1.14 0.48 2.7 0.765 1.22 0.49 2.98 0.67 Lifestyle behaviours (None as reference) Weight-reducing exercises 0.17 0.12 0.23 < 0.001 0.16 0.11 0.23 < 0.001 Lowering food intake 0.45 0.11 0.20 < 0.001 0.12 0.09 0.17 < 0.001 Adding vegetables to diet 0.26 0.19 0.36 < 0.001 0.26 0.19 0.35 < 0.001
Odds ratio (OR) by logistic regression univariate analysis Ajusted OR by multivariate logistic regression analysis by each individual variable and controled for sex
Regarding length of sleep, the odds of OW/OB were lowest among children who slept more than 11 h per day [sleeping 8–11 h (aOR =0.57, 95% CI: 0.40–0.81)], followed by those who slept between 8 and 11 h [(aOR =0.44, 95% CI: 0.22–0.87)] compared with those who slept less than 8 h.
Children with specific positive lifestyle behaviours had lower risks for OW/OB. Furthermore, the odds of developing OW/OB was lower among children who exercised for weight reduction (aOR =0.16, 95% CI: 0.11–0.23), lowered food intake (aOR = 0.12, 95% CI: 0.09–0.17), and added vegetables to their diet (aOR = 0.26, 95% CI: 0.19–0.35).
The study identified the prevalences of overweight (17.1%) and obesity (19.1%) among schoolchildren aged 11–12 years in central Hanoi from a survey conducted in 2014, and the prevalences were higher than the national averages. A prior survey of the nutritional status of children in primary schools within urban areas of Hanoi was conducted by the Vietnam National Institute of Nutrition in 2011. That previous survey included participants aged 7–9 years and found rates of overweight and obesity of 23.4 and 17.3%, respectively [[
In addition to determining the prevalence of OW/OB, our study resulted in several other findings. Children of parents with college or university degrees had the lowest risks for OW/OB. Our result was concordant with those of previous studies. Many studies in developed countries, such as the USA, Brazil, France, Denmark, and Appalachia, showed similar results as ours [[
We also found that parental OW/OB is a risk factor for OW/OB among children. This result is similar to the results of previous studies conducted in South Korea from 2007 to 2010 [[
Several studies have shown that breastfeeding contributes to preventing OW/OB in children [[
According to a meta-analysis, most studies have concluded that BW is a factor that contributes to OW/OB [[
Many studies have shown that time spent watching television is associated with an increased risk of OW/OB [[
The results of the study showed that the duration of sleeping was negatively associated with OW/OB among children. This is the same result as that of a meta-analysis [[
We evaluated self-perceived assessment of health-promoting behaviours for lifestyle improvement among children. We obtained one important finding that self-efficacy of specific positive lifestyle behaviours was strongly associated with reduced risks of OW/OB among children. There are several studies reporting the associations between self-efficacy and obesity among children [[
This study has some limitations regarding the generalizability of our findings. First, this study was a cross-sectional study. Therefore, we could not address causal relationships of variables or factors related to obesity. The potential causal relationships must be clarified by longitudinal studies. Second, this study was limited to the urban area of Hanoi, and the results may not be applicable to all populations in Hanoi; however, the results could be a reference for large cities in Vietnam, such as Ho Chi Minh, Da Nang, and Hue cities. Further studies should include students in other areas with a focus on identifying lifestyle factors that can effectively prevent and treat OW/OB. Third, we did not investigate the factors associated with our findings. We found that children of parents with college or university degrees had the lowest risks for OW/OB and that children who showed specific positive lifestyle behaviours had reduced risks of OW/OB. In the future, we need to conduct further investigations to clarify specific associated factors related to these findings. Finally, an effective educational programme should be implemented in schools to improve students' knowledge and induce behavioural changes that can contribute to reducing the prevalence of OW/OB among children in urban and rural areas of Vietnam based on our findings.
The prevalences of OW/OB among 11- to 12-year-old students in central Hanoi were quite high compared with the data from other studies in Hanoi and Ho Chi Minh City in Vietnam [[
Grants were provided from the National Center for Global Health and Medicine (28S8, 25S1) and Japan Agency for Medical Research and Development. The funders had no role in the study design, data collection and analysis, or manuscript writing.
We have obtained permission to publish full names of the people who contributed to our research and would like to express our sincere thanks to Professor Mitsuhiko Hara of the Department of Human Nutrition, Faculty of Human Nutrition, Tokyo Kasei Gakuin University, who provided us with valuable advice for performing the study; Phan Hung for his supportive English translation; Pham Thuy Linh for her general assistance; all the teachers, students, and parents from the four junior high schools that participated in this study; and to American Journal Experts for editing a draft of the manuscript.
PTPT designed the study, wrote the proposal, organized and performed the study, analyzed the data, wrote the manuscript and edited the final manuscript for publication. YM provided statistical advice and corrected the manuscript. DTKL, DVT, NTTT provided advice in the design of the study, organized and performed the study, collected the data and discussed initial ideas for writing the manuscript. BTA set up and supervised the process of blood samples collection, treatment and preservation as well as performed laboratorial tests. NQA supervised the whole study. HK designed the study, wrote the proposal, supervised the whole study and edited the final manuscript for publication. All the authors have read and approved the final manuscript.
The datasets generated and/or analysed during the current study are not publicly available but are available from the corresponding author on reasonable request.
The study protocol was approved by the Ethical Committee of Bach Mai Hospital, Hanoi, Vietnam, decision number: 529 QD-BM on May 10, 2013 and the Ethical Committee of the National Center for Global Health and Medicine, Japan, decision number: 1496 on October 1, 2013. Before the collection of questionnaire data and venous blood samples, information sheets and consent forms were distributed to parents and students by the schools. Students participating in the study agreed to provide written informed consent with written approval from their parent(s). All participants could withdraw from the study at any time without any threats or disadvantages.
Not applicable.
The authors declare that they have no competing interests.
Graph: Additional file 1. Survey Questionnaire (for students).
Graph: Additional file 2. Questionnaire for parent.
• BMI
- Body mass index
• BW
- Birth weight
• CI
- Confidence interval
• ISO
- International Organization for Standardization
• NCDs
- Non-communicable diseases
• OR
- Odds ratio
• OW/OB
- Overweight and obesity
• WHO
- World Health Organization
Supplementary information accompanies this paper at 10.1186/s12889-019-7823-9.
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By Thuy Thi Phuong Pham; Yumi Matsushita; Lien Thi Kim Dinh; Thanh Van Do; Thanh Thi The Nguyen; Anh Tuan Bui; Anh Quoc Nguyen and Hiroshi Kajio
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