Bioimpedance analysis combined with sagittal abdominal diameter for abdominal subcutaneous fat measurement

Abdominal subcutaneous fat tissue (ASFT) is an independent predictor of mortality. This prospective observational study aimed to establish a rapid, safe, and convenient estimation equation for abdominal subcutaneous fat area (SFA) using bioimpedance analysis (BIA) combined with sagittal abdominal diameter (SAD). A total of 520 adult subjects were recruited and were randomly divided into 2/3 (n = 346) and 1/3 (n = 174) to form a modeling group (MG) and a validation group (VG), respectively. Each subject's abdomen was scanned using computed tomography to obtain target variables (SFA_CT). Predictor variables for all subjects included bioimpedance index (h²/Z), anthropometric parameters height (h), weight (W), waist circumference (WC), hip circumference (HC), and SAD, along with age and sex (male =1, female = 0). SFA estimation equation SFA_BIA+SAD was established for the MG using stepwise multiple regression analysis. Cross-validation was performed using VG to evaluate the performance of the SFA_BIA+SAD estimation equation. Stepwise multiple regression analysis was applied from the MG, including SFA_BIA+SAD = 49.89 + 1.09 SAD-29.90 Sex + 4.71 W-3.63 h²/Z-1.50 h (r = 0.92, SEE = 28.10 cm², n = 346, p < 0.001). Mean differences in SFA_BIA+SAD relative to SFA_CT were -1.21 ± 21.53, 2.85 ± 27.16, and -0.98 ± 36.6 cm² at different levels of obesity (eutrophic, overweight, obese), respectively. This study did not have a large number of samples in different fields, so it did not have completely external validity. Application of BIA combined with SAD in anthropometric parameters achieves fast, accurate and convenient SAF measurement. Results of this study provide a simple, reliable, and practical measurement that can be widely used in epidemiological studies and in measuring individual SFA.