In this study, the states of obesity, physical activity, and diet of 4 th-6 th graders were examined in an agricultural area of the Tohoku region, where many pupils are driven to and from school. The physique (height, weight), physical activity level (Select 2 ; Kenz), and nutritional intake were investigated in 32 elementary school pupils for one week.The subjects showed the following characteristics : 1) A high percentage of obese pupils, 2) a small number of walking steps, and 3) a lower percentage of obese pupils than non-obese pupils participating in sports activities. Therefore, efforts to increase the physical activity level are considered to be necessary for the prevention of obesity. For this purpose, in addition to administrative measures to increase exercise opportunities in the community such as the establishment of a general sports club, local movements such as encouraging pupils to walk to school may be effective.

The purpose of this study was to examine time trend changes in the amount and type of physical activities obtained by an accelerometer and an activity record over a 20-year period in urban elementary schoolchildren. A total of 388 sixth-grade children (11–12 years old) in an elementary school in Kyoto participated in the study (n = 125 in 1999, 108 in 2009, and 155 in 2017/2018). The size and shape of the school district did not change. The school schedule was nearly the same in 1999, 2009, and 2017/2018. The children were instructed to wear an accelerometer for 5 consecutive weekdays and to keep minute-by-minute activity records with the assistance of their parents. The percentage of overweight/obese children increased with time, but the increases were not significant. The step count per day, activity energy expenditure, and physical activity level were significantly lower than they were 20 years ago, and they were significantly higher than they were 10 years ago. The time spent playing outdoors was significantly shorter than it was 20 years ago, and while it was significantly longer than it was 10 years ago. Independently from year, the time spent playing outdoors was strongly correlated with accelerometer-derived physical activity. The time spent walking to school, sleeping, studying in girls was correlated with accelerometer-derived physical activity. The factor of activity pattern related to secular changes of accelerometer-derived physical activity over the 20-year period is the time spent walking to school, sleeping in boys and the time spent club activity in girls.