A longitudinal study on differential impacts of the COVID-19 pandemic and normalized prevention and control on overweight and obese adolescents in China.

Abstract

Objective: To investigate the impact of the coronavirus disease 2019 (COVID-19) pandemic and its subsequent normalized prevention and control phase on the body mass index (BMI) and prevalence of overweight and obesity among adolescents aged 13-18 years in China, providing a basis for formulating growth and development intervention strategies in the post-pandemic era.

Methods: Using a random cluster sampling method, 120,459 adolescents aged 13-18 years from 15 junior and senior high schools across 4 districts/prefectures in Xinjiang, China, were selected as study subjects based on geographical distribution characteristics from 2017 to 2021. Height and weight were measured in strict accordance with the National Student Physical Health Standard, and physical status was classified into underweight, normal weight, overweight, obesity, and combined "overweight+obesity" based on BMI. Relevant data were analyzed using normality tests, one-way ANOVA, χ² test, and binary logistic regression, accounting for the clustered sampling design. The significance level was set as 5%.

Results: The mean BMI of adolescents aged 13-18 years in 2020 increased significantly by 0.2 kg/m² compared with previous years, while showing a declining trend in 2021 (F=104.862, P<0.001). BMI changes exhibited gender and age differences, with girls showing greater fluctuation than boys (F = 114.950, 30.063, both P < 0.001). Statistically significant differences were also observed across all age groups (all P < 0.05). Detection rates of nutritional status categories showed: compared with 2017-2019, the underweight rate decreased to 10.6% in 2020, while overweight and "overweight+obesity" rates increased to 9.5% and 12.0%, respectively (both P<0.05); compared with 2020, the underweight rate rebounded to 13.9% in 2021, while overweight and "overweight+obesity" rates decreased to 8.0% and 10.7%, respectively (both P<0.05), with particularly significant changes observed in girls and the 13-15-year-old group. Logistic regression analysis (with 2017 as reference) indicated that in 2020, the risk of underweight decreased (OR=0.668, 95% CI: 0.633-0.706), while the risks of overweight (OR=1.280, 95% CI: 1.199-1.366) and "overweight+obesity" (OR=1.364, 95% CI: 1.286-1.448) increased; in 2021, the risk of underweight increased (OR=0.917, 95% CI: 0.872-0.965), while the risk of "overweight+obesity" decreased (OR=1.201, 95% CI: 1.131-1.275), with these associations being more pronounced in girls.

Conclusion: The initial stage of the COVID-19 pandemic was associated with a significant negative impact on the weight status of Chinese adolescents aged 13-18 years, manifested by increased BMI and elevated detection rates of overweight and obesity. As prevention and control entered a normalized phase, this impact gradually diminished, with weight distribution showing a tendency to return to pre-pandemic status. Future efforts should focus on strengthening long-term dynamic monitoring of adolescent weight changes and developing and implementing precise health interventions to prevent undesirable physical status and promote the overall healthy development of adolescents.