Contribution of the BMI Level or the Body Fat Percentage Level to Bone-Mass Development in Young Women

It is unclear which body mass index (BMI) or body fat percentage level has the strongest effect on thebone mass in young women.We examined the data gathered from 233 adolescent girls in a junior high，high school，and university to ascertain the relationship between BMI or body fat percentage andbone mass.The transmission index (TI) of the calcaneus was measured using an ultrasound bone densitometer.The subjects were classified into 3 groups by BMI and body fat percentage separately. The data wasanalyzed by using the analysis of variance and an unpaired t-test.The bone mass differed significantly between each BMI group and a significant difference was observedbetween the groups associated with the body fat percentage of the Average group and the Obese group in junior high school students.There was also a significant difference between the Average group and the Obese group in both groups associated with a BMI and the body fat percentage in high school students. The subjects in the Average or the Obese group obtained their peak bone mass during high school. The subsequent reduction in bone mass following the peak level differed significantly in the Average and Obese groups. In summary，the variation of bone mass in the Average group appears to be the optimal pattern in comparison with the other BMI or body fat percentage groups. Keeping the BMI or body fat percentage level near an average level should therefore be a top priority for the prevention of osteoporosis.