Effect of the COVID-19 pandemic on the status of overweight and obesity among children and adolescents: a retrospective study in Chengdu, China


 Background: The prevalence of overweight and obesity among children and adolescents is steadily increasing and has become a public health concern. Lifestyle changes due to the COVID-19 pandemic may have an impact on the status of overweight and obesity among children and adolescents. This study aimed to analyze the effect of the COVID-19 pandemic on the status of overweight and obesity among children and adolescents. Methods: We retrospectively analyzed the children and adolescents who visited the West China Second University Hospital, Sichuan University from January 1st, 2018 to June 30st, 2020. We included obese children who met the criteria and divided them into 5 groups with 6 months as the unit according to the time of their visit. The national lockdown time was used as a segmentation point to study the changes of obesity status in the same children before and after lockdown. Results: A total of 140,526 children and adolescents visited the outpatient department from January 1st, 2018 to June 30st, 2020, and 1,740 of them were diagnosed as overweight or obese at the time of their first visit. The study found that there was a significant difference in the obesity rate among the groups (P < 0.01). However, there was no difference between January to June, 2020 and the previous period. Except for the increased incidence of VD deficiency (P < 0.01), the severity of obesity, insulin resistance and dyslipidemia of obese children did not change before and after COVID-19 (P=0.303, 0.663, 0.106, respectively). A total of 65 obese children were followed up in the outpatient department before and after COVID-19 lockdown. There were no significant differences in BMI-SDS, HOMA-IR and 25(OH)VD among obese children before and after lockdown (p = 0.626, 0.386, 0.251, respectively). Conclusions: The available evidence cannot prove that the COVID-19 pandemic affects the status of overweight and obesity among children and adolescents who visited hospitals. It may be related to the multiple effects of the COVID-19 pandemic on children.


Introduction 1
Overweight and obesity have become a global public health concern (1), and this trend is also 2 becoming more obvious in children (2). It was reported that in 2015, 12% of adults and 5% of 3 children in the world met the diagnostic criteria for obesity. Although the obesity rate of 4 children is lower than that of adults, it is rising faster than that of adults (3,4). From 1997 to 5 2015, the incidence of overweight, obesity and severe obesity of children in China increased 6 from 4.6% to 21.1%, 1.4% to 10.1%, and 0.2% to 4.0%, respectively (5). And researches have 7 shown that Obesity is associated with a variety of diseases, such as type 2 diabetes and 8 cardiovascular disease (6)(7)(8) and obesity in childhood is associated with an increased risk of 9 cardiovascular death in adulthood (9). And early detection of cardiovascular problems in obese

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Studies have reported that the implementation of lockdown measures during COVID- 19 18 pandemic reduces physical activity in adults and leads to an increase in body mass index(BMI) 19 (13). For children and adolescents, although some scholars believe that school closures during 20 COVID-19 pandemic may result in reduced physical activity and increased unhealthy diets, 21 resulting in weight gain (14), which is also found in clinical practice, others believe that the 22 pandemic may reduce the risk of childhood obesity (15). The relevant research in this area has 23 not been reported. Therefore, we retrospectively analyzed the children who visited the West

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We included children or adolescents who first visited the outpatient during the study period 31 and were diagnosed as overweight or obese according to the diagnostic criteria.The exclusion 32 criteria were obese children with conditions that may affect the BMI, such as central precocious 33 puberty, growth hormone deficiency dwarfism, chronic kidney disease, Autoimmune and 34 chronic kidney diseases requiring hormone therapy, etc. Further, we included obese children 35 who were followed up at the outpatient during the study period and visited the outpatient 36 before and after the COVID-19 pandemic national lockdown time(January 23st, 2020), 37 respectively.

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Data collection: We collected basic information about children and adolescents, such as sex, 39 date of birth, date of diagnosis, age at diagnosis, height, weight, comorbidities through the 40 hospital case system. We divided the study period into 5 groups with 6 months as the unit, and 41 each obese child was divided into 5 groups according to the date of diagnosis. All 1 measurements of children's height and weight were carried out and recorded by 2 specially-trained personnel in accordance with standards. BMI is a person's weight in kilograms 3 divided by the square of height in meters and the formula is weight (kg) / [height (m)]2.

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BMI-SDS was calculated based on height and weight in kilograms/meter2 and adjusted 5 for sex and age according to Chinese growth curves (16). We collected the laboratory results of 6 children and adolescents through the hospital laboratory system, such as fasting blood

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Those with approximate normal distribution were analyzed by paired t test, and those without 42 were analyzed by wilcoxon signed ranks sum test. A p-value＜0.05 was considered statistically 43 significant.    However, there was no statistical difference between each group and January to June, 11 2020 (Table 1) 12       Counting data were tested by chi-square test, and measurement data were analyzed by one-way analysis of variance.
The situation of obese children at different time periods: 1 The VD deficiency rate of obese children was significant higher in January to June, 2020 than in 2 2018 and July to December, 2019(p ＜ 0.01)(    Chi-square test was used.  Chi-square test was used.
Obese children before and after lockdown:    There was no significant change in the obesity rate of children visiting the hospital from 8 January to June, 2020 compared with that in the previous period. In addition to the increased 9 incidence of VD deficiency, the severity of obesity, insulin resistance and dyslipidemia in obese 10 children did not change. Therefore, it has not been demonstrated that the pandemic affects 11 the obesity status of children and adolescents visiting the hospitals.

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Although there was a slight increase from January to June, 2020 in childhood obesity  (30), which could lead to lower obesity rates in the spring and higher obesity rates in the winter.

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For obese children who were followed-up in outpatient department and visited the outpatient 8 department before and after lockdown respectively, there was a slight decrease in BMI-SDS,

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Obesity may increase the incidence of VD deficiency in children (32)(33), which may be due to   Ethics approval and consent to participate 24 25 The study has been granted an exemption from requiring ethics approval and informed 26 consent by the Ethics Committee of West China Second University Hospital of Sichuan

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University because of following factors.Firstly, the COVID-19 pandemic is a public health 28 emergency that cannot be predicted in advance. Secondly, we collected patient's anonymous 29 data retrospectively and were unable to track the anonymous data. Thirdly, we only used data 30 from normal clinical activity during the study and promised not to misuse it.

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Consent for publication 33 Not applicable. 34 35 Availability of data and materials 36 The datasets used and/or analysed during the current study are available from the 37 corresponding author on reasonable request. 38