Effectiveness of Screen-Time Interventions on BMI, Daily Screen Use and Diet Behaviours in Preschool Children: A Systematic Review and Meta-Analysis of Randomised Controlled Trials.

OBJECTIVE: This study aimed to systematically review and quantitatively synthesise the effects of screen-time-focused interventions on body mass index (BMI), daily screen time and diet-related behaviours among preschool children. METHODS: A PRISMA 2020-compliant systematic review and meta-analysis of randomised controlled trials (RCTs) involving children aged 2-6 years was conducted. Eligible trials targeted screen use via parent education, home-based programs, technology-assisted restriction or digital/app-based interventions, reporting ≥ 1 outcome (BMI, daily screen time or diet). Searches were performed in PubMed, Web of Science, Embase and Scopus. Risk of bias was assessed with RoB 2. Random-effects meta-analyses with Hartung-Knapp adjustment were performed, and heterogeneity (I2, τ2), sensitivity analyses, funnel plots and meta-regression were used to evaluate robustness and moderators. RESULTS: Ten RCTs including approximately 2800 preschool children were analysed. Screen-time interventions resulted in a small but statistically significant reduction in BMI compared with controls (MD = -0.18 kg/m2; 95% CI - 0.33 to -0.03; I2 = 92.7%). Reductions in daily screen time favoured intervention groups but were not statistically significant (MD = -27.2 min/day; 95% CI - 66.9 to 12.5; I2 = 99.2%). No consistent improvements were observed for diet-related behaviours. Sensitivity analyses confirmed the robustness of BMI findings. Meta-regression indicated that BMI effects were attenuated in studies with higher proportions of girls, whereas screen-time reductions were greater among older preschool children. CONCLUSIONS: Screen-time interventions in preschool children yield modest BMI benefits but inconsistent effects on screen use and diet. Age- and sex-related differences in responsiveness highlight the need for tailored, family-centred intervention strategies.