Abstract
<title>Abstract</title> <p>Purpose To examine the relative accuracy of skinfold (SKF)-derived body fat percentage (%Fat) compared with commonly used laboratory-based methods and to quantify the extent to which observed disagreement is attributable to variability among criterion techniques. Methods Eighty-seven apparently healthy adults completed a single laboratory visit. %Fat was assessed using SKF and compared with underwater weighing (UWW), bioimpedance spectroscopy (BIS), dual-energy X-ray absorptiometry (DXA), and a four-compartment (4C) model. Absolute error (AE) was calculated between SKF and each criterion method. A disagreement ratio quantified observed error relative to inter-method variability. Linear mixed-effects models were used to estimate the proportion of error attributable to criterion selection. Results SKF-derived %Fat (18.0 ± 8.6%) was significantly lower than UWW (22.3 ± 8.2%), BIS (23.0 ± 8.1%), DXA (26.2 ± 8.8%), and 4C (21.6 ± 8.3%) (p < 0.001), but was strongly correlated with each method (r = 0.88–0.95). Differences among UWW, BIS, and DXA accounted for approximately 40–60% of the observed disagreement between SKF and individual criterion methods. Inclusion of criterion method in the model increased explained variance and reduced residual error, indicating that a substantial portion of observed disagreement was attributable to variability among criterion techniques. Conclusions A meaningful proportion of the error attributed to SKF-derived %Fat reflects differences among criterion methods rather than limitations of the technique itself. These findings suggest that method comparison outcomes are inherently dependent on the selected reference, supporting the use of consistent methodology and longitudinal monitoring rather than reliance on single-point estimates.</p>