We measured bone mass using calcaneal ultrasound and studied the dietary/lifestyle habits of 283 first- to third-grade junior high school students in Kanagawa Prefecture using a self-reported questionnaire. As a result of comparing the three grades, no significant differences were found among them in terms of the percentage of students who slept fewer hours and ate breakfast/dinner alone. Furthermore, the percentage of students who answered “rarely” when asked how frequently they drank milk was high among third-year students. The rate of first- to third-year students with a Z score (an indicator of bone mass, compared with the standard value for the same sex and age) of less than 90％ was 20.5％ (58 students). There were significant differences among the grades for students with a Z score of less than 90％. Although there was no relationship between frequency of milk consumption and bone mass in all subjects, the percentage of students who belonged to sports clubs in school or the community was higher in the high Z score group compared with the low Z score group.
Third-year students in junior high school had several problems related to dietary/lifestyle habits and bone mass that first- and second-year students generally didn't have, and so a support system is necessary for improving their dietary/lifestyle habits to prevent osteoporosis.
