Health-Related Behaviors and BMI Across Three School Years: Annual Bayesian Network Patterns During the PETICA Childhood Obesity Prevention Program

Background/Objectives: This study examined annual probabilistic network structures among dietary habits, health-related attitudes, lifestyle behaviors, and body mass index (BMI) during implementation of the PETICA school-based program. Methods: This was a three-year prospective, uncontrolled school-based intervention with repeated measurements of the same cohort in Grades 2–4. The BMI analytic samples comprised 915 pupils in Grade 2 (461 boys, 454 girls; mean age 7.9 ± 0.4), 840 in Grade 3 (429 boys, 411 girls; mean age 8.9 ± 0.5), and 684 in Grade 4 (341 boys, 343 girls; mean age 9.9 ± 0.4). BMI was recalculated from measured body mass and height and used as the continuous network outcome. BMI-for-age percentiles were retained for age- and sex-specific descriptive classification and sensitivity analysis. Separate score-based Bayesian networks were estimated for each grade. Network stability was assessed using 200 nonparametric bootstrap samples, with stable adjacency defined as a bootstrap frequency of at least 50%. Results: Fruit and vegetable intake formed a stable adjacency in all three grades, with bootstrap frequencies of 100.0% in Grade 2, 98.0% in Grade 3, and 99.0% in Grade 4. The sex of the pupil and computer/video-game use were stably connected in Grades 3 and 4 (100.0% in both grades). Stable connections among health-related attitudes were more prominent in later grades. In Grade 4, at-home breakfast consumption was connected with water intake (57.5%) and vegetable intake (52.0%). No behavioral adjacency with continuous BMI reached the prespecified 50% stability threshold in any grade. The largest subthreshold behavior–BMI signal was observed for at-home breakfast consumption in Grade 4 (39.0%). Conclusions: Selected relationships among reported health-related behaviors were reproducible across annual assessments, whereas direct behavior–BMI connections were year-specific and did not reach the stability threshold. The greater integration of attitudes and healthy habits in later grades is compatible with cumulative, age-adapted health education, but the absence of an untreated comparison group prevents attribution of these patterns to PETICA. The findings do not establish causal effects or program effectiveness, but may contribute to hypotheses generation for future evaluations of multi-component school-based obesityprevention programs.