Age-Group Differences in BIA-Derived Body Composition and Device-Generated Visceral Fat Rating in a Clinical Cohort

Background/Objectives: Body mass index (BMI) is widely used to classify weight status, but it does not reflect fat distribution, muscle mass, or bone mass. Bioelectrical impedance analysis (BIA)-derived visceral fat rating (VFR) is a device-generated estimate of visceral adiposity. This study assessed age- and gender-related differences in anthropometric and BIA-derived body composition parameters, with particular attention to the relationship between BMI classification and VFR. Methods: This cross-sectional study included consecutive adults admitted to a single plastic surgery clinic over three months. Waist and hip circumferences were measured, waist-to-hip ratio was calculated, and body composition was assessed using a Tanita BC-420 MA analyzer. Associations between age, BMI, and BIA-derived parameters were assessed using Spearman's rank correlation. BMI categories were cross-tabulated with VFR categories, and multivariable linear regression was used to assess VFR in relation to age, BMI, and gender. Results: The study included 326 patients. Mean BMI was higher in men than in women (27.6 ± 4.33 vs. 26.4 ± 5.07; p = 0.006), and men also had higher VFR (12.8 ± 6.15 vs. 7.75 ± 3.74; p < 0.001). Older age groups had higher VFR values, ranging from 2.16 ± 1.82 in participants aged 18-29 years to 14.3 ± 5.0 in patients aged ≥ 80 years. BMI and VFR were strongly correlated, but BMI categories did not fully correspond to VFR categories. Manufacturer-defined elevated VFR was observed in 5 patients with normal BMI and 24 patients with overweight, whereas 26 patients classified as obese had a manufacturer-defined normal VFR category. Conclusions: In this surgical cohort, older age groups had markedly higher VFR values than younger groups despite relatively modest differences in BMI. Because VFR is a device-generated estimate rather than a direct measure of visceral adiposity, these cross-sectional findings should be interpreted cautiously. Validation against established reference methods is needed before drawing broader clinical conclusions.