Abstract
BACKGROUND: Behavioral modification programs have improved body composition, dietary behavior (DB), and physical activity (PA). However, there is limited evidence on the effectiveness of these programs among overweight high school students in rural areas of Thailand. Therefore, this study aimed to examine the effects of a school-based behavioral modification (SBM) program on these factors among high school students with overweight. Study Design: This study employed a randomized controlled trial. METHODS: The study was conducted from November 2022 to May 2023 among overweight high school students. A total of 100 overweight students were randomly assigned to either an intervention (n=50) or a control (n=50) group. The intervention group received an SBM, while the control group received the usual educational program. The chi-square test, independent-samples t-test, Mann-Whitney U test, ANOVA, and Cochran's Q test were used to analyze data. RESULTS: Both groups were female (72.0%), with a mean age of 17.03 years. At the follow-up, the intervention group demonstrated significant improvements in DB and PA and a reduction in sedentary behavior compared to the control group (P<0.05). Additionally, statistically significant differences were observed between the intervention and control groups regarding biceps (P=0.001), triceps (P=0.031), and waist circumference (P<0.001). CONCLUSION: The SBM effectively increased students' PA, improved DBs, decreased sedentary behavior, and resulted in changes in body composition. These findings indicated that SBM programs are useful for healthcare providers or teachers to promote healthy behaviors among students and can be applied in related research in different contexts and situations.