Nutritional and behavioral determinants of overweight and obesity among school-aged children in Shandong Province, China: evidence from a large-scale cross-sectional study.

BACKGROUND: Childhood overweight and obesity are pressing global health challenges with rising prevalence in China. Shandong Province, as a populous and economically developed region, provides a critical context for understanding regional patterns and determinants. METHODS: A cross-sectional survey was conducted among 83,436 children aged 9-12 years from 155 schools in 16 cities (September-November 2025). Anthropometric measurements and validated questionnaires were used to assess weight status, demographics, family environment, and lifestyle factors. Overweight/obesity was classified using International Obesity Task Force (IOTF) cut-offs. Logistic regression identified associated risk and protective factors. RESULTS: The prevalence of overweight/obesity was 19.0%. Rates were higher in boys than girls (19.9% vs. 18.2%, p < 0.001) and increased with age (11-year-olds 20.4% vs. 9-year-olds 18.0%, p < 0.001). Urban children had slightly higher prevalence than rural peers (19.6% vs. 18.7%, p = 0.002). Factors independently associated with overweight/obesity included parental overweight/obesity (OR = 1.18, 95% CI: 1.10-1.26), maternal gestational diabetes (OR = 1.53, 95% CI: 1.36-1.71), and high birth weight (OR = 1.16, 95% CI: 1.09-1.24). Lifestyle behaviors were strongly associated: <1 h/day physical activity increased risk, while >1.5 h/day was protective (OR = 0.83, 95% CI: 0.79-0.87); >8 h sleep reduced risk (OR = 0.66, 95% CI: 0.60-0.72); >3 h/day screen time (OR = 1.10, 95% CI: 1.02-1.20) and >3 h/day homework (OR = 1.49, 95% CI: 1.38-1.62) elevated risk; frequent fruit/vegetable intake was protective, whereas fast-food consumption >3 times/week increased risk (OR = 1.12, 95% CI: 1.05-1.20). CONCLUSION: Childhood overweight/obesity in Shandong Province is influenced by demographic, familial, and lifestyle factors. Findings highlight the importance of multilevel interventions-targeting family health behaviors, maternal metabolic management, school-based physical activity promotion, and community nutrition policies-to curb the rising burden of obesity.