About 10 per cent of fourth-year primary school students in Kagawa Prefecture who received health checks last year showed signs of abnormal liver function, according to prefectural government sources.
Among the children whose blood samples were checked, about 10 per cent also showed abnormal figures related to lipid levels, and about 10 per cent showed abnormal blood-sugar levels.
Medical researchers believe that this is largely due to the children's dietary habits and inadequate physical exercise. They now want to carry out a nationwide survey on the issue.
The research covered 16 cities and towns among 17 municipalities in the prefecture, where blood sample checks on the fourth-graders were conducted.
Data about liver functions and lipid and blood-sugar levels was collected from about 8,264 children whose parents or guardians had agreed to the research, accounting for about 96 per cent of the total.
Concerning liver function, levels for three substances, including Alanine transaminase (ALT), were checked. Readings for ALT tend to rise when the burden on the liver is greater.
Of the boys, 12.4 per cent showed abnormal results in at least one of the three tests, with comparable results seen in 9.5 per cent of the girls.
Readings for lipids - such as total cholesterol and neutral fat - were abnormal in 10.2 per cent of boys and 11.5 per cent of girls.
The percentage of boys with abnormally high figures of hemoglobin A1c (HbA1c) was 12 per cent, and that of girls was 10.9 per cent. High HbA1c figures indicate a continued presence of high blood-sugar levels.
Levels to be considered average for children in each of the tests were decided by the prefectural government based on domestic medical research and the opinions of doctors around the nation.
The prefectural government's research has found that many of the children with abnormal results have lifestyle habits such as eating when they are not hungry, eating quickly, playing games for extended periods in a day, and not doing physical exercises.