Acceleration in BMI gain following COVID‐19 restrictions. A longitudinal study with 7‐ to 10‐year‐old primary school children

BACKGROUND: The ramifications of COVID‐19 restrictions might accelerate the already rising proportion of children with overweight or obesity. OBJECTIVES: To assess the association between COVID‐19 restrictions and changes in body mass index (BMI) and the proportion of children with overweight or obesity. METHODS: Cohort study with baseline measurements in September 2019 (prior to COVID‐19 restrictions) and follow‐up in June 2020, September 2020, and March 2021 at 12 primary schools in Austria. The height and weight of 738 children aged 7 to 10 years were measured and age‐ and sex‐specific national and international standardized values were calculated. Changes over time were analysed by analysis of variance. RESULTS: Mean BMI(IOTF) standard deviation scores (SDS) increased by 0.24 (95% CI, 0.21–0.28) between September 2019 and March 2021. The proportion of children with overweight or obesity increased from 20.7% to 26.2% during this period (p < 0.001) using national reference values—EQUI BMI(AUT)—comparable results were observed. Simultaneously, the height(AUT) SDS increased by 0.06 (95% CI, 0.05–0.08) with a larger increase in girls (+0.11; p < 0.001) than in boys (+0.03; p = 0.19). CONCLUSIONS: COVID‐19 restrictions were associated with accelerated increases in mean BMI and the proportion of children with overweight or obesity. The increase in height SDS in girls calls for further investigations.