Moderate-to-vigorous Physical Activity And Non-academic Sedentary Time In Relation To Obesity Prevalence Among Korean Adolescents: A Study Of Korea Youth Risk Behavior Surveys (2013-2023)

The prevalence of obesity among Korean adolescents has doubled over the past decade. Non-academic sedentary time (NAST) and moderate and vigorous physical activity (MVPA) are known factors affecting obesity risk; however, Korean adolescents exhibit very low levels of physical activity alongside high amounts of sedentary time. PURPOSE: To investigate the association between NAST and adherence to MVPA guidelines with obesity prevalence among Korean middle and high school students from 2013 to 2023. METHODS: Data from the Korea Youth Risk Behavior Web-based Survey included 609,441 participants after excluding those with missing data on height, weight, NAST, MVPA, and covariates. Obesity was defined as body mass index (BMI (kg/m2)) at or above the 95th percentile using age-specific growth charts. Self-reported NAST was categorized as ≤2 hours/day or > 2 hours/day, while MVPA guidelines were defined as at least 60 minutes/day moderate-intensity physical activity daily, along with more than 3 days/week of vigorous physical activity. The independent and combined associations of NAST and MVPA with obesity prevalence were assessed using multivariable logistic regression. RESULTS: The overall obesity rate among adolescents was 9.5%. Overall adherence rate of NAST and MVPA was 30% (40.5% for middle school students, 28.3% for high school students) and 5.5% (6.6% for middle school students, 4.3% for high school students). Higher NAST (>2 hours/day) (Odds Ratio (OR) = 1.29, 95% Confidence Interval (CI) 1.27-1.32) was associated with higher odds of obesity, compared to lower NAST (≤ 2 hours/day). For MVPA, meeting guidelines significantly reduced the odds of obesity (OR = 0.76, 95% CI 0.73-0.79) compared to those not meeting the guidelines. The association between obesity and each of NAST and MVPA was consistent across all grade levels. In combined analysis, meeting both MVPA guidelines and NAST (≤2 hours/day) was associated with lower odds of obesity compared to meeting only MVPA, only NAST, or neither group. CONCLUSIONS: Meeting both MVPA guidelines and maintaining low sedentary time was associated with the lowest odds of obesity compared to neither group across all grade levels. Therefore, to reduce obesity risks in students, minimizing NAST and increasing MVPA are essential.