Background: University students in Iraq face rising obesity risk linked to physical inactivity, prolonged sedentary behavior, insufficient sleep, and academic stress. Longitudinal evidence examining the combined influence of these behaviors on weight status in Iraqi universities remains limited. Objective: This study examined six-month longitudinal associations of physical activity, sedentary behavior, sleep duration, and perceived stress with body mass index and percentage body fat among Iraqi university students. Methods: A prospective multi-behavioral study was conducted at six public universities in Iraq. Six hundred undergraduate students aged 18–25 years were followed monthly during one academic semester. Validated questionnaires and smartphone-based applications assessed health behaviors, while standardized procedures measured body mass index and body fat. Data were analyzed using descriptive statistics, correlations, regression models, and repeated-measures analysis. Results: Overweight and obesity prevalence reached 63.7%. Most students met minimum physical activity recommendations, yet sedentary time was high and sleep duration was suboptimal. Sleep duration showed a small inverse association with body mass index and body fat and was the only behavior differing significantly across body mass index categories. Males exhibited higher body mass index, whereas females had higher body fat percentage. Conclusions: Integrated context-sensitive health strategies addressing sleep habits, sedentary behavior, and academic lifestyle factors may support obesity prevention.
