Changes in accelerometer-measured physical activity and sedentary time among young people in Belgium between 2014-15 and 2022-23

This study examined changes in accelerometer-measured physical activity (PA), sedentary time (ST), and adherence to international PA guidelines among Belgian children and adolescents aged 5–17 years between 2014-15 and 2022-23. Data were obtained from the Belgian Food Consumption Survey (2014-15: n = 1043; 2022-23: n = 790). Associations between time spent in light PA (LPA), moderate-to-vigorous PA (MVPA), and ST on week- and weekend days, and survey year were analysed using design-based t- or Kruskal-Wallis tests. The association between guideline adherence (≥ 60 min MVPA/day on average and vigorous PA ≥ 3 days/week) and survey year was analysed using design-based Pearson’s chi-squared tests. Analyses were stratified by age and sex. No significant changes were observed in weekday ST, while ST increased on weekend days among adolescents aged 10–13 years (+ 23 min/day, P = 0.034), girls aged 5–9 years (+ 24 min/day; P = 0.023) and boys aged 10–13 years (+ 40 min/day; P = 0.054). Time spent in LPA and MVPA on weekdays increased by 16 ( P = 0.004) and 6 min/day ( P = 0.002), respectively, among girls while remaining stable among boys. On weekend days, MVPA showed a non-significant increase among girls (+ 4 min/day; P = 0.056), whereas LPA showed a non-significant decrease among boys aged 10–13 years (− 22 min/day; P = 0.066). Overall, guideline adherence remained stable (37.6% vs. 39.9%). Among girls, estimated adherence increased (from 23.4% to 30.4%), but this difference did not reach statistical significance ( P = 0.072). Despite some favourable changes, most participants did not meet PA guidelines, highlighting the need for continued surveillance and targeted interventions.