Individualized body geometry correction factor (K_B) for use when predicting body composition from bioimpedance spectroscopy

Objective. Prediction of body composition from bioimpedance spectroscopy (BIS) measurements using mixture theory-based biophysical modelling invokes a factor (K_B) to account for differing body geometry (or proportions) between individuals. To date, a single constant value is commonly used. The aim of this study was to investigate variation inK_Bacross individuals and to develop a procedure for estimating an individualizedK_Bvalue.Approach.Publicly available body dimension data, primarily from the garment industry, were used to calculateK_Bvalues for individuals of varying body sizes across the life-span. The 3D surface relationship between weight, height andK_B, was determined and used to create look-up tables to enable estimation ofK_Bin individuals based on height and weight. The utility of the proposed method was assessed by comparing fat-free mass predictions from BIS using either a constantK_Bvalue or the individualized value.Results.ComputedK_Bvalues were well fitted to height and weight by a 3D surface (R² = 0.988). Body composition was predicted more accurately compared to reference methods when using individualizedK_Bthan a constant value in infants and children but improvement in prediction was less in adults particularly those with high body mass index.Significance.Prediction of body composition from BIS and mixture theory is improved by using an individualized body proportion factor in those of small body habitus, e.g. children. Improvement is small in adults or non-existent in those of large body size. Further improvements may be possible by incorporating a factor to account for trunk size, i.e. waist circumference.