Submitted to: Nutrition
Publication Type: Peer reviewed journal
Publication Acceptance Date: 1/13/1999
Publication Date: N/A
Citation: Interpretive Summary: There is increasing interest among nutritionists and clinical investigators in determining the composition of the body of humans. Although traditional methods, such as measurements of skinfold thicknesses and underwater weighing, provide estimates of fat and fat-free masses, other body components, such as bone and muscle mass, are perhaps more appealing because of interest in osteoporosis and aging. A relative new method, dual x-ray absorptiometry, provides the opportunity to determine fat, muscle and bone. We compared determinations of fat, muscle and bone determined with this new method and with chemical analyses in a group of pigs. Although the new method gave values for muscle and muscle plus bone that corresponded with the chemical measurements, there was a discrepancy for the fat determinations. We presumed that differences in body thicknesses would explain the differences in fat between the method, but we found that thickness was not related to these differences. The explanation of this discrepancy is that the new method does not determine fat within bones. These findings indicate that the new method is acceptable for routine determinations of human body composition. This information will be useful for researchers who want to determine human body composition, particularly muscle and bone, safely and quickly.
Technical Abstract: Evidence of the validity and accuracy of dual x-ray absorptiometry (DXA) to measure body composition is limited. We compared DXA estimates made in prone and side positions with measurements of chemical composition of 20 pigs (10 barrows and 10 gilts) weighing 52 to 113 kg. Barrows and gilts had similar body composition. DXA yielded similar estimates of body composition in prone and side positions. DXA estimates of body composition were significantly correlated with reference compositional values (r**2 = 0.927 to 0.998). Although no significant differences were found for determinations of body weight, fat mass (FM), fat-free mass (FFM), bone-free, fat-free mass (BFFFM) between DXA and chemical determinations, DXA significantly underpredicted percent fat (% fat), and underestimated FM by 20% and overestimated FFM and BFFFM by 6 and 9%, respectively. Differences between individual determinations of FM by chemical analyses and DXA were significantly correlated with mean values; similar results were shown for % fat. However, no significant correlations were found between the differences for weight, FM, % fat, FFM and BFFFM and measurements of carcass breadth (19 to 28 cm) and width (15 to 25 cm). Total errors in determination of DXA body compositional variables were similar with body thicknesses less than and greater than 24 cm. These findings indicate that DXA is a valid and accurate method for determination of soft tissue composition, particularly FFM and BFFFM.