Trends and Associated Factors of Obesity in Preschool Children in Northwest China: a population-based cohort study from 2012 to 2024

Childhood obesity is a growing public health concern globally and in China, with long-term health and economic consequences. Evidence suggests that early life, particularly the first 1,000 days, is a critical window for obesity prevention. This study aimed to assess the prevalence, temporal trends, and associated risk factors of obesity among children under three years of age in Shaanxi Province from 2012 to 2024. Data were obtained from the National Children’s Nutrition and Health Surveillance System (NCNHSS), a population-based registry covering urban and rural sites in Shaanxi. A total of 8,201 children aged 0–3 years were included. Anthropometric and sociodemographic data were collected through standardized physical examinations and caregiver interviews. Temporal trends were analyzed using Joinpoint regression. Multivariable logistic regression was used to identify risk factors for obesity at 36 months. The overall obesity prevalence at 36 months was 1.91%, with a fluctuating trend between 2012 and 2024. A significant decline was observed in rural areas, followed by a temporary increase in 2021, coinciding with the COVID-19 pandemic, and a subsequent reduction. In contrast, urban children exhibited a modest upward trend. Most children classified as obese at 36 months had already become overweight or obese by 18 months. Low socioeconomic status was strongly associated with increased obesity risk in both rural (AOR = 2.15; 95% CI: 1.54–2.99) and urban settings (AOR = 1.83; 95% CI: 1.29–2.60). In rural areas, children whose mothers worked in agriculture had significantly higher odds of obesity (AOR = 2.30; 95% CI: 1.23–4.30), as did those born small for gestational age (AOR = 1.63; 95% CI: 1.02–2.60). Among urban children, prolonged breastfeeding without appropriate complementary feeding was associated with increased obesity risk (AOR = 1.41; 95% CI: 1.01–1.99). Additionally, cesarean delivery (AOR = 1.41; 95% CI: 0.98–2.04) and grandparent-led caregiving (AOR = 1.51; 95% CI: 0.94–2.42) in rural areas were associated with marginally higher odds of obesity, though these associations did not reach statistical significance. Although obesity prevalence among children in Shaanxi remains relatively low, early onset and socioeconomic disparities persist. Targeted interventions during the first 1,000 days, particularly for low-income and high-risk families, are essential. Policies should focus on nutrition education, support for appropriate infant feeding, and early growth monitoring to prevent obesity in early childhood and reduce long-term health risks.