Effect of the bone mineral content variation on the body fat ratio computation in young adults / 体力科学

ABSTRACT

Bone mineral content (BMC), fat weight (FAT) and lean tissue weight (LTW) were determined by dual-energy X-ray absorptiometry (DEXA) in 20 young adults of both sexes who were performing habitual exercise. From these data, body weight, lean body weight (LBW) and the percentage of BMC relative to LBW (BMC%LBW) were obtained. First, body density based on a two-component model (D<SUB>2</SUB>) was calculated using the values of FAT and LBW of the subjects and the fat and lean densities of the Reference Body, Then percentage body fat (%Fat<SUB>2</SUB>) was calculated using the formula of Brozek et al. The body density for a three-component model (D<SUB>3</SUB>) was then determined from the values of FAT, BMC and LTW of the subjects, and the fat, bone mineral and lean tissue densities of the Reference Body. Percentage body fat (%Fat<SUB>3</SUB>) was also calculated in the same manner as %Fat<SUB>2</SUB>. Analysis of the data indicated that (1) females had higher values of BMC%LBW than males, and that (2) subjects whose %Fat<SUB>2</SUB> exceeded %Fat<SUB>3</SUB> by more than 1% were exclusively females whose BMC%LBW values were more than 6.1%. In contrast, those whose %Fat<SUB>2</SUB> was lower than %Fat<SUB>3</SUB> by less than -1% were exclusively males who had BMC%LBW values less than 5.2%. It is concluded that male subjects develop their muscles more than their bones with habitual exercise, which results in a lower BMC%LBW value than in females, and that for those with BMC%LBW values exceeding 6.1% (females) or less than 5.2% (males), %Fat calculation from body density using the formula of Brozek et a1. will produce an error of more than 1% if BMC%LBW is not considered.