Study protocol for a pragmatic randomized controlled trial evaluating coarse-cereal intake intervention for obesity prevention among primary school students in suburban Beijing, China

Background: The rising prevalence of childhood obesity poses a significant public health challenge in China, with rates among primary school students increasing from 6.8% in 2002 to 19% in 2020. Concurrently, coarse-cereal intake-a source of dietary fiber and bioactive compounds with potential protective effects against obesity-has declined markedly. School-based interventions represent a feasible strategy to address this issue. This protocol describes a cluster-randomized pragmatic controlled trial (pRCT) aimed at evaluating the effectiveness of a comprehensive intervention to increase coarse-cereal intake for obesity prevention among Chinese primary school students. Methods: A two-arm pragmatic cluster-RCT will be conducted in public primary schools in Huairou District, Beijing. Two schools will be randomly assigned to intervention or control groups, with 400 students (grades 3-4, aged 8-12 years) enrolled. The intervention group will receive a daily 50 g coarse-cereal substitution in school meals, aligned with Chinese dietary guidelines, alongside a multi-level nutrition education program targeting students, parents, and school staff. The control group will continue standard practices. Primary outcomes include changes in body mass index standard deviation score (BMI-SDS), body composition, waist circumference, and blood pressure, assessed at baseline, 3 months, and 6 months. Secondary outcomes encompass metabolic indicators and gut microbiota profiles in overweight/obese subgroups. Data will be analyzed using mixed-effects linear models, accounting for cluster effects. Implementation fidelity will be monitored through quantitative and qualitative methods. Discussion: This trial will address a critical evidence gap by testing a culturally adapted, school-based intervention to promote coarse-cereal consumption. If effective, the findings will inform the integration of coarse cereals into national student meal policies, contributing to sustainable obesity prevention strategies in China. The study design emphasizes practical implementation through a socio-ecological framework, with potential for scalability. Clinical trial registration: Identifier ChiCTR2500114773.