Sedentary Behavior and Physical Activity: Contrasting Effects on Body Composition in Public vs. Private School Students Aged 12 to 18 Years (P1)

Background and Study Aim: Childhood and adolescent obesity are a pressing global health issue with significant implications for long-term health outcomes. Understanding the impact of sedentary behavior (SB) and physical activity (PA) on body mass index (BMI) is crucial for developing effective interventions. This study examines the divergent effects of PA and SB on BMI among public and private school students in Al-Hasa, Saudi Arabia. Material and Methods: A cross-sectional study design was employed, involving 1,510 students (946 public, 564 private) aged 12–18 years. Anthropometric measurements, PA levels, and SB scores were assessed using validated questionnaires. Statistical analyses were conducted to explore associations between SB, PA, and BMI across school types. Results: Public school students demonstrated higher SB scores (p = 0.032, ES = 0.111) and lower PA levels (p < 0.001, ES = 0.265) compared to private school students. Despite this, private school students exhibited higher rates of overweight and obesity (p = 0.044, ES = 0.106). In public schools, increased PA levels were significantly associated with lower BMI (B = -0.091, p < 0.001), while age (B = 0.026, p < 0.001) and greater SB scores, particularly video gaming (B = -0.128, p < 0.001) and laptop use (B = -0.055, p = 0.020), were positively correlated with higher BMI. In contrast, private school students showed a significant positive relationship between overall SB scores and BMI (B = 0.033, p = 0.001), with laptop (B = -0.131, p < 0.001) and video game usage (B = -0.126, p < 0.001) being the strongest predictors. However, no significant association was found between age (B = -0.002, p = 0.840) and PA levels (B = 0.008, p = 0.564) and BMI in private schools. Conclusions: The findings highlight the influence of school environments on adolescent health behaviors. Public schools showed stronger links between PA, SB, and BMI, whereas private schools demonstrated a greater impact of SB on BMI. These results underscore the need for tailored interventions to reduce sedentary behaviors and promote physical activity. Addressing infrastructure disparities, enhancing physical education programs, and fostering healthier lifestyles are critical for combating adolescent obesity in Saudi Arabia.