This cluster-randomized trial will develop and test an intervention technology for school-aged children. The program combines digital health technology and personalized behavior intervention through a WeChat platform.

Our main question is: Does this integrated approach improve obesity related outcomes and behaviors in children?

Investigator will:

• Compare children receiving the program with those receiving usual care.
• Track physical measures and health behaviors to measure effectiveness of intervention.
• Evaluate the program's safety, implementation process, and cost-effectiveness. Findings will determine if this approach should be expanded to more communities.

This study is a one-year cluster randomized controlled trial (cRCT) to be conducted in 10 eligible primary schools. The schools will be randomly allocated to either the intervention group or the control group in a 1:1 ratio.

The technical core of this research involves the development of a multi-level collaborative health management technology system based on a WeChat platform. This platform will serve as the core intervention technology, providing functional support to the intervention group schools, their students, and parents.

Students in the control group schools will receive routine health education and physical examination procedures during the trial period.

To evaluate the effectiveness of this intervention technology, outcome measure data will be collected at multiple time points. All participating students will undergo physical measurements and health behavior questionnaire surveys at baseline (T0) and at the end of the intervention period (T1, i.e., 12 months post-baseline). The changes in primary and secondary outcome measures from baseline (T0) to the end of the intervention (T1) will be compared between the intervention and control groups.

Furthermore, to assess the long-term sustainability of the intervention effects, investigator plan to conduct follow-up surveys annually at 24 months (T2) and 36months (T3) post-intervention for both the intervention and control group students. Generalized linear mixed model or Generalized Estimating Equations (GEE) will be constructed to longitudinally analyze the differential trajectories of health outcomes between the two groups, thereby comprehensively evaluating the immediate effects and long-term sustainability of this integrated intervention technology.

Inclusion Criteria:

• Schools will be selected based on the consent of primary leadership, demonstrated cooperation, and availability of necessary personnel (e.g., school health professionals). Classes will be limited to grades 2 and 3, with teachers showing strong willingness to collaborate. Both parental informed consent and child assent are required for participation.

Exclusion Criteria:

• Schools will be excluded if they cater to special populations (e.g., schools for children with disabilities), are involved in other obesity-related interventions within the specified timeframe, or plan to close or relocate within two years. Children will be excluded if they have histories of major organ diseases (e.g., cardiac, pulmonary, hepatic, or renal conditions), special diets (e.g., vegetarian), pathological eating disorders, physical limitations affecting activity, or obesity due to endocrine disorders or medication side effects.

Individual participant data (lPD) will not be shared publicly due to ethical considerations. in accordance with the study's ethical approval and informed consent procedures, the data contain potentially sensitive personal health information and are protected to ensure participant confidentiality and privacy. Data access is therefore restricted to authorized research personnel only and cannot be made publicly available.

Randomization will be performed after the baseline survey. The assessors measuring children's health indicators(e.g.,weight and height) will be blinded at follow up phases.