{'fraction_non_alphanumeric': 0.03646948035270953, 'fraction_numerical': 0.037839226093656364, 'mean_word_length': 4.920932589964521, 'pattern_counts': {'":': 0, '<': 2, '<?xml version=': 0, '>': 0, 'https://': 0, 'lorem ipsum': 0, 'www.': 0, 'xml': 0}, 'pii_count': 0, 'substrings_counts': 0, 'word_list_counts': {'cursed_substrings.json': 2, 'profanity_word_list.json': 0, 'sexual_word_list.json': 0, 'zh_pornsignals.json': 0}}
Unfavorable progression of obesity in children and adolescents due to COVID‐19 pandemic: A school‐based survey in China

Abstract Objective The Chinese government decisively imposed nationwide confinement in response to the COVID‐19 outbreak. This study aimed to evaluate the impact of the COVID‐19 pandemic on the progression of obesity in children and adolescents in Changshu, China. Methods Based on the Health Promotion Program for Children and Adolescents (HPPCA), which is a prospective cross‐sectional and school‐based study, BMI assessed in seven consecutive years (2014 to 2020) among children and adolescents aged 6 to 17 years in Changshu city was extracted. The standardized BMI z scores (zBMI) and prevalence of obesity between 2020 (after COVID‐19 home confinement) and the previous 6 years were compared among age‐specific subgroups and between sexes. Results The mean number of participants per year was 29,648. The overall mean zBMI drastically increased from 0.29 in 2019 to 0.45 in 2020, resulting in a rise of 0.16 (95% CI: 0.14‐0.18); the prevalence of obesity substantially elevated to 12.77% in 2020 (versus 10.38% in 2017), with an acceleration of 2.39% (95% CI: 1.88%‐2.90%). Of note, these increases were more likely to be observed in boys and those 6 to 11 years old. Conclusions The COVID‐19 pandemic seemed to exacerbate the obesity epidemic among pediatric populations in Changshu, China.


Study area and population
This study was based on the data of seven consecutive years (from 2014 to 2020) from the HPPCA. Detailed descriptions of the HPPCA were reported previously (14). In brief, in order to investigate the health status of school-aged children, the HPPCA was designed to annually assess the health status (including BMI) of all potential students aged 6 to 17 years from elementary, middle, and high school (grades one to twelve) in the Suzhou region of China. Chronically ill or disabled children were not included.
In particular, students in the third year of middle and high school (ninth and twelfth graders) who would take other special physical examinations for school entrance were not included in this study, as their data are currently not available. In general, students' physical examination was taken in general hospitals, centers for disease prevention and control, or community health care centers.
In the current study, we focused on Changshu city, which is a county-level city in Suzhou. In accordance with the Chinese National Survey on Students' Constitution and Health, which was a national surveillance every 5 years (15), stratified cluster random sampling was selected to keep equality of selected numbers in every grade in the current study. As the second-largest city for immigrants, the population of Suzhou increases rapidly.
In order to keep representativeness and consistency of students in these years, selected schools should meet the following criteria: from 2014 to 2020, school did not change address, merge other schools, or be merged by other schools. Finally, 12 primary schools, 8 junior high schools, and 4 senior high schools were selected. Schools were divided by urban or rural area according to their addresses.

Study Importance
What is already known?
► The COVID-19 pandemic may deteriorate children's health behaviors and thereby increase weight gain.

What does this study add?
► Compared with the highest value in previous years (2014 to 2019), the overall mean zBMI drastically increased to 0.45 in 2020 (from 0.29 in 2019), and the prevalence of obesity substantially elevated to 12.77% in 2020 (ver-

Ethics, consent, and permissions
For the recruited participants, informed consent forms in writing duly signed by their guardians were collected before their examination. This study was approved by the Ethics Committee of Suzhou Center for Disease Prevention and Control (No. SZJK2020-XW001).

Measurements and obesity definition
All the health examinations of the HPPCA were taken during September and December, both in previous years and during the COVID-19 pandemic in 2020. The heights (nearest 0.1 cm) and weights (nearest 0.01 kg) were measured with stadiometers and calibrated digital scales in light clothing and without shoes. BMI was calculated (BMI = kilograms/meter squared) and then transformed into a zBMI corresponding to the age-and sex-specific reference outlined by the WHO (16). Overweight and obesity were defined according to the WHO Child Growth Standards (16).
In 2020, owing to the COVID-19 pandemic, all the examiners and students were required to conduct temperature monitoring (below 37.3°C), present a health code, and wear medical masks during the screening. All examiners were trained to perform the professional

TA B L E 2 Prevalence of obesity in school-aged children and adolescents in each year
Prevalence, % (n) physical examination wearing gloves, and students were requested to stand at a safe distance from each other (at least 1 m) when queuing.

Statistical analysis
Annual zBMI data are presented as mean (SE). zBMI and prevalence of obesity among the seven consecutive years were compared by using one-way ANOVA and χ2 test, respectively; for comparing the prevalence of obesity in 2020 with the highest prevalence in 2014 to 2019, a two-proportion z test was performed. Additionally, subgroup differences of change in zBMI and obesity prevalence were compared by examining interaction effects through standard methods (17,18). All statistical analyses were performed using SAS software (version 9.4; SAS Institute, Inc., Cary, North Carolina). A two-sided p value < 0.05 was considered statistically significant.

RE SULTS
A total of 207,536 children and adolescents were included in this study, with age ranging from 6 to 17 years old. The number of participants in each year is shown in Supporting Information Table S1, and the mean number of participants per year was 29,648. The age and sex distribution of the population is shown in Supporting Information Figure S1, and the numbers of included boys and girls in each of the screening years were quite close. zBMI and prevalence of obesity are illustrated in Table 1 and Table 2. In general, during the annual screenings conducted from 2014 to 2019, zBMI and prevalence of obesity steadily and slowly increased, and these values of boys were consistently higher than those of girls.
zBMI substantially increased in 2020 compared with previous years (2014 to 2019), regardless of sex ( Figure 1). A similar trend was revealed for obesity prevalence ( Figure 2). It was also found that zBMI in the 7 years was significantly different in each of the age groups (Supporting Information Table S2). Compared with the highest value during 2014 to 2019, obesity prevalence increased in 2020 in all the age groups, but only the ages of 6 to 11 and 15 to 16 showed statistical significance (Supporting Information Table S3). (95% CI: 0.14-0.18). The acceleration in zBMI change in the age category of 6 to 11 was 0.19, which was significantly larger than that of the age category of 12 to 17 (0.11, p < 0.001); rise in zBMI change in urban areas (0.10) was comparable to that in rural areas (0.14, p = 0.066); whereas the elevation in zBMI change in boys (0.18) was significantly higher than in girls (0.13, p = 0.014). In addition, the prevalence of obesity substantially elevated to 12 Also, the differences significantly differed between age categories and regions (Figure 4). When comparing values between 2020 and 2019, the changing patterns were generally not altered.

DISCUSS ION
Owing to the COVID-19 confinement, both overall mean zBMI and obesity prevalence significantly increased among children and adolescents aged 6 to 17 years in Changshu, China. In particular, it was found that boys and 6-to 11-year-old children were more sensitive to COVID-19 confinement regarding obesity aggravation. Our results strongly support the speculations that pandemic-related confinements were unfavorably related to weight status (9).
The COVID-19 pandemic has had a negative impact on the obesity burden in the Chinese population. Similar to our findings, the COVID-19 Impact on Lifestyle Change Survey, which included 10,082 youths in China, 28.01% of whom were high school students, reported that both the BMI and the prevalence of overweight/ obesity had increased after lockdown (19). Other Chinese studies, mainly for adults, also concluded that significant changes in body weight occurred during the lockdown period (20,21). In addition, the unfavorable influence of the COVID-19 pandemic on childhood obesity was observed in Korea (22), Italy (23), Greece (24), and the United States (25).
Exercise and diet are particularly related to obesity (4). During the home confinement, students' sleep was irregular, their indoor and sedentary activities increased, and their sport and outdoor activities decreased (19,26,27). It was also found that children often had an unhealthy diet at home during the COVID-19 pandemic lockdown, such as an increased intake of snacking, sugary drinks, and meals (26,28). Importantly, the months of January and February in 2020 were also the time of the Spring Festival in China, when people tend to consume more high-fat and high-calorie food than usual, which also created an unprecedented obesogenic environment. Besides, the COVID-19 confinement has increased isolation, psychological distress, anxiety, and depression, which may result in night and stress eating (29). Furthermore, extensively prolonged screen times (both for academic activity and leisure) during the lockdown (19) may also contribute to obesity due to lack of physical activity and increased energy intake (30). Moreover, potential adverse childhood events caused by significantly increased domestic violence during the COVID-19 pandemic might lead to eating disorders and thereby obesity in the pediatric population (31,32).
Specifically, the elevation of BMI and prevalence of obesity during the COVID-19 pandemic were more obvious in 6-to 11-year-old younger children. We speculate this age disparity could be explained by the following reasons. School is an important locale for physical education classes and extracurricular physical activity (33), and children lose access to almost all forms of supervised sources of physical activity as a result of school closures (34 In the current study, boys seemed to be more susceptible to adiposity than girls during the COVID-19 confinement. Studies conducted before the COVID-19 pandemic showed that boys spent more time on physical activity than girls, especially moderate and vigorous physical activity (36,37). However, during COVID-19 confinement, a larger drop of physical activity and a higher increase of sedentary behavior were observed in boys compared with girls (23,38). What's more, Chinese girls prefer a slender shape traditionally, especially during puberty, so they are more likely to control their weight than boys (39,40). In a word, the gender disparity in physical self-concept and adherence to unhealthy lifestyles during COVID-19 pandemic may contribute to the observed results. Thus, it may be critical to develop and implement gender-specific preventive guidelines for obesity during the confinement.
On March 11, 2020, WHO announced that the novel COVID-19 virus had become a global pandemic. Although there F I G U R E 2 Prevalence of obesity by gender for children and adolescents aged 6 to 17 years during the 7 years of screenings F I G U R E 3 BMI z score changes from prepandemic period to 2020 between subgroups F I G U R E 4 Difference of obesity prevalence from prepandemic period to 2020 between subgroups