Skin tissue dielectric constant in women with high body fat content

Abstract

Background Skin tissue dielectric constant (TDC) measurements at a frequency of 300 MHz are used to assess skin properties in many conditions. Impacts of patient obesity on these values are unknown, and its quantitative assessment was the goal of this research. Materials and Methods Women in a weight loss program (N = 32) had TDC measured on forearm, biceps, neck, jowl, and submental regions along with measurements of total body fat (TBF), water (TBW), intracellular water (ICW), and extracellular water (ECW) via multi‐frequency bioimpedance. Group age (mean ± SD) was 40.0 ± 11.6 years (20‐70 years) with body mass index (BMI) of 31.8 ± 6.7 Kg/m2 (23.0‐49.9 Kg/m2). For analysis, subjects were divided into those with BMI < 30 Kg/m2 (subgroup A, n = 16) vs ≥30 Kg/m2 (subgroup B, n = 16). Results Tissue dielectric constant at forearm and biceps decreased significantly (P < .001) with increasing depth from 0.5 to 1.5 to 2.5 mm but TDC values and their inter‐side ratios did not differ between subgroups A and B at any measured site. Although correlations between TBW, ECW, and ICW were significant (P < .001), there was no dependence of TDC values on any of these parameters. Conclusions Previously unknown TDC values for obese persons are provided and based on subgroup analyses suggest that skin TDC values in overweight and obese persons are not confounded by variables such as TBW and TBF. Further, since inter‐side ratios and their SD’s yielded thresholds for forearm and biceps similar to those established for women with normal BMI, use of these clinical inter‐arm TDC ratios now is extended to include a wider BMI range.

Medical Applications of Skin Tissue Dielectric Constant Measurements

“…The correlations were found to be greatest at the deepest measurement depth. When TDC was measured in overweight or obese women, a similar depth dependence was obtained for measurements made on the forearms and biceps [63]. TDC differences between women who were overweight and obese were not apparent, possibly due to a threshold for TDC dependence on body fat percentage.…”

Breast Cancer-Related Lymphedema Assessed via Tissue Dielectric Constant Measurements

“…This means that in regions of the body where there is more subcutaneous fat, particularly at deeper levels, TDC values are typically lower. This has been demonstrated in several studies [41][42][43][44]. An evaluation of 40 healthy women in whom forearm TDC was measured bilaterally and compared to total body water percentage showed a positive correlation between total body water percentage and total body fat percentage when TDC was measured to a depth of 5 mm [40].…”

“…An evaluation of 40 healthy women in whom forearm TDC was measured bilaterally and compared to total body water percentage showed a positive correlation between total body water percentage and total body fat percentage when TDC was measured to a depth of 5 mm [40]. When such measurements were done on women who were overweight or obese, a similar depth dependence of TDC was reported [42]. However, not all anatomical sites show a decrease in TDC values with increasing measurement depth.…”

Measuring Breast Cancer-Related Lymphedema

“…In some tissues, TDC values depend on measurement depth because of depth-dependent tissue heterogeneity (96,97). Increased fat with increasing depth tends to lower the TDC value due to low water content of fat (87,98). Variations in TDC values are also expected based on sex (99-101), age (102,103), body habitus (104), and at different anatomical sites along the arm (105,106).…”