The four-compartment models in body composition: data from a study with dual-energy X-ray absorptiometry and near-infrared interactance on 815 normal subjects.

With the aim of studying body composition according to a four-compartment model in different age groups of healthy subjects, total body water (TBW), body fat (BF), lean body mass (LBM), and total-body bone mineral content (TBBMC) were estimated with dual-energy x-ray absorptiometry (DEXA) and near-infrared interactance in 308 normal males and 507 normal females aged 15 to 83 years. Subjects were divided into 5-year groups up to the age of 50, and then into 10-year groups. In both sexes, BF showed a positive correlation with age (P < .001) and was higher in females aged 40 to 44 compared with younger groups. LBM decreased with age only among males (P < .05). A similar finding was observed with TBW. TBBMC values did not differ between sexes in the 15- to 19-year-old group, and were greater in males in the remaining age groups. This parameter did not vary among females until menopause, and decreased in the 50- to 59-year-old group (P < .001) and from the age of 60 onward (P < .001). Height decreased (P < .001) and weight increased with age (P < .001). Both in male and female groups height and weight correlated with TBBMC (P < .001). When corrected for weight, TBBMC did not vary except in men older than 50, who showed lower values (P < .005). When corrected for height, TBBMC only changed in women aged 30 to 34 and 35 to 39.(ABSTRACT TRUNCATED AT 250 WORDS)

Determinants of total-body and regional bone mineral content and density in postpubertal normal women.

Some investigators consider body fat the main determinant of bone mass in women, and others, weight. Although genetics may be the primary determinant of peak bone mass, modifiable secondary factors such as nutrition and hormone exposure may significantly affect bone mass accretion during the second decade of life. To determine the principal determinants of bone mass, we analyzed total and regional bone mass (by dual-energy x-ray absorptiometry), weight, height, percentage body fat, and lean body mass in a group of 50 young women ranging in age from 14 to 18 years. Total-body bone mineral content, total-body bone mineral density, and total-body bone mineral density corrected for height, analyzed by multiple correlation, were not related to percentage body fat, although percentage body fat did correlate with the regional bone mineral content of the trunk (P < .001), legs (P < .01), and pelvis (P < .001). Lean body mass correlated with total-body bone mineral content and density, total-body bone mineral density corrected for height (P < .001), and regional bone mineral content of the trunk (P < .05), arms (P < .01), and legs (P < .001), but not with regional bone mineral content of the pelvis and head. Weight correlated significantly (P < .001) with all bone mass measurements except regional bone mineral content of the head, where the significance was P less than .05. Similar results were obtained by multiple regression analysis. These results indicate that weight, not body fat, is the main determinant of bone mass in postpubertal women.