Secular Trends in Overweight and Obesity among Japanese Children and Adolescents

Abstract

The prevalence of childhood obesity has increased worldwide. It is a major public health concern in Japan as well. There are, however, few studies on the trends of childhood obesity in Japan. PURPOSE: To examine the trends of overweight and obesity in Japanese youth using international BMI cutoffs. METHODS: In Japan, a large-scale nationwide, cross- sectional survey has been carried out every year under the direction of the Ministry of Education, Culture, Sports, Science and Technology. Standing height and body mass are measured in the survey, and the frequency matrices on height (every 1 cm) and mass (every 1 kg), but not the raw data, have been published. For the present study, we used the matrix data for 5-, 8-, 11-, 14-, and 17-year-old males and females from the 1978, 1983, 1988, 1993, 1998, and 2003 surveys. The body mass index (BMI) in each cell of the matrix was calculated from the body mass (kg) of the cell divided by square of the standing height (m) of the cell. Then the BMI of each cell was compared with sex- and age-specific international BMI cutoffs presented by Cole et al (2000). When the BMI of a cell exceeded the international cutoffs for overweight or obesity, we identified the subjects included in that cell as overweight or obese, respectively. The prevalence of overweight and obesity were obtained from the sum of frequencies included in the cells where the BMI exceeded the international cutoffs. RESULTS: The percentage (%) of overweight and obesity increased over the 25 years, as shown in the Table. The highest percentages were seen at age 11 for overweight and at age 8 for obesity in 2003, for both males and females. Mean values for standing height, body mass, and BMI gradually increased over time. However, the modes of BMI were almost constant during the 25 years, suggesting that the increasing percentage of youth having high BMI above a cutoff is not attributed to secular increase in body size or secular trends towards earlier maturation.TableCONCLUSION: A substantial increase over time in overweight and obesity was observed in Japanese youth, particularly for younger children aged 8 and 11 years.