EVALUATION OF NEAR-INFRARED INTERACTANCE FOR ASSESSMENT OF SUBCUTANEOUS AND TOTAL-BODY FAT

Objective: Near infra-red interactance (NIRI) has been used for assess ment of total body fatness, but its relationship with composition at t he measurement site is not clear This study examines the relationship of interactance with subcutaneous adipose tissue and muscle thickness as well as total body fat content. Design: (i) Validation of NW by com parison with subcutaneous tissue thicknesses from ultrasound. (ii) Cro ss-validation of techniques for estimation of body fat content. Settin g: Laboratory. Subjects: (i) 54 young adults (27 male and 27 female) a nd (ii) 63 middle-aged men. Interventions: Measurements of subcutaneou s adipose tissue thickness and muscle thickness using ultrasound near infra-red interactance (Futrex 5000) and skinfold thicknesses were mad e at five sites in young adults. In middle-aged men total body fat was assessed by densitometry, NIRI and skinfold thickness. Measurements w ere made in duplicate by a single trained observer. Results: Interacta nce measurements were related to subcutaneous adipose tissue thickness , although the relationship varied according to measurement site (r = 0.09 at anterior thigh to 0.78 at biceps; P = 0.31 to <0.0001). Muscle thickness explained additional variance in interactance only at bicep s in women. Subcutaneous adipose tissue thickness correlated better wi th skinfold thickness (r = 0.56 to 0.92; P = 0.002 to <0.0001) than wi th interactance. Mean difference in fat mass from densitometry +/- 95% limits of agreement was -1.61 +/- 7.68 kg for NIRI and -2.84 +/- 6.56 kg for skinfold thickness in middle-aged men. NW tended to underestim ate higher (and overestimate lower) levels of fatness.Conclusions: NIR I performed no better than skinfolds in assessment of either subcutane ous or total body fat. Sponsorship: This work was supported by the Bri tish Heart Foundation.