The PKU-SMART is a cluster randomized controlled trial conducted in Jinan, Shandong Province, China. This preventive intervention study aims to develop and evaluate a comprehensive obesity intervention framework for preschool children that integrates digital health technologies, multi-sectoral collaboration, and tiered management strategies. The effectiveness and cost-effectiveness of this approach will be assessed.

In the past four decades, the number of children and adolescents with obesity worldwide has increased tenfold, making childhood overweight and obesity one of the most pressing public health issues. In China, the prevalence of overweight and obesity among children under six years old in China has reached 10.4%.

Children with obesity are more likely to develop health problems than their normal-weight peers. The health impacts of childhood obesity often persist into adulthood, significantly increasing the risk of cardiovascular diseases, endocrine and respiratory disorders, cancers, and other chronic conditions. Therefore, the prevention and management of childhood obesity are critical for promoting both immediate and long-term health.

However, current intervention strategies often face challenges such as inconsistent outcomes, poor adherence, and a lack of theoretical foundation. There is a pressing need to develop more effective, scalable, and sustainable approaches.

To address this gap, we propose an intervention(PeKing University Smart Monitoring And Responsive Technology for early childhood health, PKU-SMART), a cluster-randomized preventive trial targeting preschool children. This study will develop and evaluate an innovative, digital health-supported, multi-sector, tiered intervention system aimed at improving preschoolers' health behaviors, reducing obesity prevalence, and supporting long-term weight management.

Kindergarten-Level Inclusion Criteria:

• The kindergarten's principal or headmaster consents to participate in the study, and the school demonstrates a high level of cooperation. Required personnel, such as a school health care provider, are available.
• The total number of children in the middle and senior classes (approximately ages 4-6) exceeds 100.
• Teachers and parents of the selected classes demonstrate good compliance and willingness to cooperate with project implementation.

Kindergarten-Level Exclusion Criteria:

• Special kindergartens, such as part-time institutions or schools for children with special needs.
• Kindergartens that have participated or plan to participate in other obesity-related intervention projects within the past year or upcoming year.
• Kindergartens scheduled for closure or relocation within the next two years.

Child-Level Inclusion Criteria:

• The child's primary caregivers can proficiently use smart phones.
• The child is expected to remain enrolled in the same kindergarten for at least one year.
• Parents or legal guardians provide written informed consent for participation.

Child-Level Exclusion Criteria:

• Obesity caused by genetic disorders, endocrine diseases, central nervous system damage, or long-term medication use.
• History of significant diseases affecting major organs such as the heart, lungs, liver, or kidneys (e.g., congenital heart disease, hypertension, asthma).
• Children on special diets, including vegetarianism.
• Children diagnosed with pathological eating disorders or conditions that impair physical activity.

Individual participant data (IPD) 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 childrens' health indicators will be blinded at follow-up phases.