RELIABILITY OF NEAR-INFRARED INTERACTANCE BODY-FAT ASSESSMENT RELATIVE TO STANDARD ANTHROPOMETRIC TECHNIQUES

We examined the repeatability of near-infrared interactance (NIR) body fat determination as compared with that of body mass index (BMI), wai st-to-hip ratio (WHR), and waist girth. Thirty-nine volunteers (16 men , 23 women) had percent body fat (%BF) measurements made with a portab le NIR device as well as the standard anthropometric indices of height , weight, waist girth, and hip circumference. Frame size and physical activity levels were also determined. For each participant, three inde pendent measurements of each index were made by two trained readers du ring a 2-week period. The two readers varied significantly in their me asurement of %BF and hip circumference. The variability in %BF was lar gely due to differences between the first and the second measurements, and only for one of the readers. Second and third measurements were n ot statistically significantly different for either reader, suggestive of a training effect. Variance component calculations revealed that t he reliability of NIR is 95.3%, compared with 99.9% for BMI; 93.4% for waist girth; and 82.4% for WHR, with the majority of the remaining va riance accounted for by the method itself. We conclude that the NIR me thod has good repeatability, with low intra- and interobserver variabi lity, provided that readers are carefully trained. However, the NIR de vice offers little advantage in reliability over conventional measures of adiposity such as waist girth or BMI, and requires additional inpu t of weight, height, frame size, physical activity level, age, and gen der data to calculate %BF. Associations of NIR and other anthropometri c indices with cardiovascular risk factors in this population will pro vide additional insight into the merit of NIR body fat assessment.