Author(s): AU, W., FONG, D., WONG, S., CHAN, D., CAPIO, C., YU, C., WONG, S., CHEN, Y., THOMPSON, W., SIU, P., Institution: THE UNIVERSITY OF HONG KONG, Country: HONG KONG, Abstract-ID: 1319

INTRODUCTION:
Pediatric obesity rate has risen sharply globally, driven mostly by declined physical activity (PA), a major obesity driver, with 35 million children under 5 being overweight or obese. Long-term threats are posed to their physical, mental, and social health, including increased non-communicable diseases (NCD) risks in adulthood. As 80% obesity cases develop before 6, early childhood is a critical window for prevention. Yet, despite over 50% affected children residing in Asia, most evidence stems from Western settings and older children where culture and body composition differs. Thus, this study examined the effectiveness of a school-based PA intervention on preventing obesity in Hong Kong preschoolers.
METHODS:
This is an on-going two-armed accessor-blinded cluster randomized controlled trial with a final sample size of 3300 preschoolers from 110 schools. Children were randomized into intervention and control groups based on schools. School-based PA program is delivered as twice weekly 75-minute game-based PA class, making up to 2.5 hours extra PA, on top of the usual curriculum with regular 2.5 hours PA. The exercise dose is benchmarked to the World Health Organization guidelines, reaching 60 min moderate-to-vigorous PA per weekday by averaging the weekly 5 hours. Adiposity and body composition were measured at the start and end of a 10-month school year. Linear mixed models were used to estimate treatment effects.
RESULTS:
1941 preschoolers from 77 schools were included in the preliminary analysis [1015 intervention, 926 control; mean age=5.23 years (SD 0.37); 883 girls]. Prevalence of overweight and obesity were 4.55% and 2.96%. PA intervention had significantly attenuated increase in waist circumference (ß=-0.83; 95% CI -1.13 to -0.54; p<0.0001) and body fat mass (-0.11; -0.18 to -0.04; p=0.0017), while reduced fat percentage (-0.46; -0.70 to -0.22; p=0.0002), even after covariates adjustment. No significant effects were found on weight and BMI, which could be due to increases in fat-free mass (p=0.0442) and muscle mass (p=0.0676). Subgroup analysis revealed potential gender differences on waist, where significant reduction was only found in girls (p=<0.0001), but not boys (p=0.0837).
CONCLUSION:
This study confirmed that a school-based PA intervention can effectively attenuate adiposity increase in a large, population-representative cohort of Chinese preschoolers. As early adiposity predicts obesity trajectory and cardiometabolic risks, findings underscore the critical role of early-life PA on promoting long-term health and reducing public healthcare burden, especially through delaying premature adiposity rebound. By standardising exercise dose to global guidelines, a major gap arising from prior heterogeneous designs is addressed to facilitate scalable integration into preschool curricula. Results at trial completion will elucidate potential sex differences of the impact of PA on adiposity.