Relationship of Optical Density and Skinfold Measurements: Effects of Age and Level of Body Fatness

Abstract

We examined relationships between skinfold (SKF) and optical density (ΔOD) measurements across age and levels of body fatness (%BF) for 151 women, 20 to 72 years. There were significant (p < .05) relationships between ΔODs and SKFs at all sites, except the thigh. The interaction (SKF × Age) was significant (p < .05) for pectoral and biceps ΔODs. Slope comparisons indicated the relationships for younger (29 years) and older (59 years) women differed significantly from zero and each other (p < .05). Analysis of SKF × %BF interactions revealed that relationships between SKFs and ΔODs at the pectoral and biceps sites for leaner (22% BF) women differed significantly from zero (p < .05) and were larger than those for obese (39% BF) women (p ≤ .05). Thus, the relationship between SKFs and ΔODs is stronger for younger and leaner women compared to older and fatter women. These findings may reflect differences in fat layering due to age or body fatness and provide insight as to why the manufacturer's near-infrared (NIR) equation significantly underestimates the %BF of obese women.