Changes in obesity and lifestyle behaviours during the COVID‐19 pandemic in Chinese adolescents: A longitudinal analysis from 2019 to 2020

BACKGROUND: Since December 2019, the coronavirus disease 2019 (COVID‐19) has become a global pandemic. Currently, the COVID‐19 pandemic is still ongoing. What changes have taken place in the obesity and obesity‐related lifestyle behaviours of adolescents during the first year of the COVID‐19 pandemic? OBJECTIVE: This study aims at analysing the changes in obesity and lifestyle behaviours of Chinese adolescents before and 1 year after the outbreak of the COVID‐19 pandemic, providing evidence for the global strategies to respond to the impact of the COVID‐19 pandemic on adolescent obesity. METHODS: Physical examinations and student health and influencing factors questionnaires were conducted among 6047 adolescents aged 11–16 years by health professionals in Shanghai, China, before the COVID‐19 pandemic (September–November of 2019) and 1 year after the outbreak of the COVID‐19 pandemic (September–November of 2020). Paired [Formula: see text] tests, paired t‐tests or Wilcoxon signed‐rank test was used to evaluate the changes in the obesity prevalence, BMI and lifestyle behaviours from 2019 to 2020. RESULTS: 1 year after the outbreak of the COVID‐19 pandemic, the obesity prevalence of Chinese adolescents rose from 14.2% to 15.4% (p < 0.01), mainly because of the increase in boys. And the average BMI increased from 20.3 to 21.2 kg/m(2) (p < 0.01). Their lifestyle behaviours have also significantly changed. The mobile screen time increased from 0.25–1.50 h/day to 0.33–2.00 h/day (p < 0.01). The proportion of adolescents who participated in MVPA for ≥60 min/day on all 7 days during the past week dropped from 14.4% to 11.7% (p < 0.01). The generalized estimation equation analysis indicated that adolescents who participated in MVPA for ≥60 min/day on all 7 days had a lower likelihood of having obesity. Boys with computer time ≥2 h/day and girls with mobile screen time ≥2 h/day or TV time ≥2 h/day had a higher likelihood of having obesity. CONCLUSION: This study found that 1 year after the outbreak of the COVID‐19 pandemic, the BMI and obesity prevalence of Chinese adolescents increased and obesity‐related lifestyle behaviours have also changed.