The aim of the present study was to identify obesity risks in the lifestyles of schoolchildren. The subjects included 478 boys 438 girls aged from 6 to15 years. Obesity, breakfast intake, sleep time and exercise frequency were subjected to the logistic regression analysis and the meta-analytical summery by sex and age. The mean body mass index (BMI) increased with age for all subjects except 7-years-old boys and 15-years-old girls. Breakfast intake and sleep time decreased with age. Exercise frequency increased with age. We conducted a meta-analytical summary of the logistic regression analysis, and found a significant correlation between obesity and exercise frequency in 13-15-years-old boys. One results indicated indicated that the decrease in the exercise frequency is the risk of obesity for 13-15-year-old boys. The lifestyles of schoolchildren change with age, and distributions of lifestyle-related variables are not constant. For such an inconsistent target, the meta-analytical summary for all subjects based on a multiple logistic regression analysis for each group is useful.