Objective: To investigate the effects of lifestyle factors on overweight among Japanese adolescents.
Methods: We studied 5753 junior high school students (2842 boys and 2911 girls) aged 12 to 13 years. The students were residents of Toyama prefecture, Japan and completed a questionnaire about their height, weight, and lifestyle factors, in June and July 2002. Subjects with a body-mass index (BMI) higher than age- and sex-specific cut-off points were defined as obese. Parental overweight was defined as a BMI of 25 or higher. Logistic regression analysis was used to examine associations between lifestyle factors and overweight.
Results: Skipping breakfast, eating quickly, excessive eating, physical inactivity, and long hours of TV watching were positively and significantly associated with overweight in both sexes. There was a negative association between snacking and overweight in girls (P<0.001); no such association was found in boys (P>0.05). Nighttime snacking was negatively associated with overweight in boys and girls (P<0.05). Extended video game playing (>or=2 hours; OR=2.00, P=0.012) and short sleep duration (<7 hours; OR=1.81, P=0.004) were significantly associated with overweight in girls only. The respective risks of overweight that derived from the subjects' fathers and mothers were 2.0 and 2.5 times, respectively, in boys and 1.9 and 3.0 times in girls.
Conclusions: Parental overweight, skipping breakfast, eating quickly, excessive eating, long hours of TV watching, long hours of video game playing, physical inactivity, and short sleep duration were associated with adolescent overweight. Furthermore, there were significant negative associations between adolescent overweight and snacking in girls and nighttime snacking in both sexes.