Collective Effect of Physical Activity and Television Watching on the Risk of Obesity in Korean Adolescents

Obesity in youths has become a topic of interest in Korea. The intention of this research is to display the joint effect of physical activity (PA) and inactivity on obesity in Koreans aged 12 to 18. There were 73,836 subjects (38,909 males, 34,927 females) who participated in the 2007 Korea Youth Health Risk Behavior web-based survey. Participants were classified into nine PA-inactivity groups according to Korea's National Health Promotion Plan 2010. The obesity group included the obese and overweight groups, which were defined by BMI (BMI for age exceeding the 85th percentile or ≥25). The reference group was the high PA and low inactivity group. Logistic regression was used to assess the joint consequence of PA and inactivity on the odds of obesity within the controlling age. Overall, the possibility of obesity increases with longer TV watching in boys and girls. But physical activity showed a reasonable association with obesity in boys, but it didn't happen with girls. In the joint effect, boys who did not exercise vigorously at all had an increased risk of obesity regardless of their TV watching level (OR 1.350-1.411). In the hard exercising girl group, high inactivity is concerned with a low risk by contraries (0.622-0.479). These results highlight the importance of understanding the complex mechanism of obesity behavior.