Wei Jia Wu ^1,2 Ping Hao Chen ^1,2 Xue Lu Lei ^1,2 Zhenning Huang ^1,2 Chen Wang ^1,2 Chun hui Zhang ^1,2 Ping Wang ^1,2 Chui can Huang ¹ Qing Luo ¹ Lichun Fan ^1,2*

• ¹ Hainan Women and Children's Medical Center, Haikou, China
• ² Hainan Medical University, Haikou, Hainan Province, China

Background and Aims: Childhood obesity leads to significant health risks, emphasizing the need for effective preventive measures during the preschool years. However, comprehensive studies on overweight and obesity among preschool children in Hainan Island, China's largest free-trade zone, are lacking. This study assessed the prevalence of overweight and obesity in preschool children across Hainan Island using Chinese, World Health Organization (WHO), and International Obesity Task Force (IOTF) criteria, and explored potential influencing factors.Methods: We conducted a cross-sectional survey of children aged 3-6 years across 18 cities and counties in Hainan Island. The survey involved anthropometric data collection and questionnaires on children’s information and sociodemographic characteristics of their parents/guardians. We recorded each child's height and weight and calculated their body mass index (BMI). The z-score for BMI-for-age was calculated using the WHO-recommended Anthro and AnthroPlus software, and diagnoses of overweight and obesity were determined according to Chinese, WHO, and IOTF criteria. The chi-squared test, t-test, or rank-sum test were applied to analyze baseline characteristics. Potential factors influencing overweight and obesity were analyzed using multifactor binary logistic regression.Results: The prevalence of overweight and obesity among preschool children in Hainan Island was 11.30% based on the Chinese criteria, significantly higher than the 5.80% and 5.40% rates observed according to the WHO and IOTF criteria, respectively (χ² = 12870.368, P<0.001). After multifactorial adjusted analyses, we found that having overweight parents, family incomes over 100,000 Yuan, active eating habits, and higher birth weights increased the risk of overweight and obesity among preschool children in Hainan Island.Conclusion: The prevalence of overweight and obesity among preschool children in Hainan Island was lower than in other regions. Given that growth and development metrics for children under 7 are generally lower in Hainan Island than international standards, using Chinese criteria proved more accurate in detecting overweight and obesity in this region. Based on identified risk factors, future preventive measures can target reducing the risk of overweight and obesity in preschool children in Hainan Island.