Abstract

Skin tissue dielectric constant in women with high body fat content

Harvey N. Mayrovitz1, Jessica Forbes2, Adithi Vemuri2, Katelyn Krolick2, Samantha Rubin2. Skin Res Technol. 2019;00:1–8.

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 interside 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.

Main findings

• N= 32
• Body composition parameters were determined using the Inbody 570 (Biospace, Inc Seoul, Korea). This device  uses impedance measurements made at multi-frequencies (5, 50, 250, and 500 kHz) to determine total        body fat (TBF),  total     body     water   (TBW),  intracellular water (ICW), and extracellular water (ECW) among other body segment
• Tissue dielectric constant used three different probes were used to achieve effective measurement depths of 0.5, 1.5, and 2.5 mm at two arm sites.
• Face and neck measurements were only made to a depth of 1.5 mm only. TDC measurements were done bilaterally except for the submental site.The sites were as follows: anterior forearm (6 cm distal  to the antecubital fossa (A), medial biceps (6 cm superior to the medial epicondyle (B), neck (3 cm lateral to the laryngeal prominences (C), jowl area of the face (1 cm lateral and 2 cm inferior to the right and left oral commissures, (D) and submental region        (E). Sites were measured in the order of A          through E with bilateral measurements  completed prior to moving  to the next  Arm measurements were made first to a depth of 0.5 mm, then 1.5 mm and lastly to 2.5 mm.
• The results showed that although ECW was highly correlated with both TBW and ICW, neither of these were correlated with TDC values measured at any depth. The practical implications of this finding suggest that when skin TDC is measured in overweight or obese individuals, the values measured are unlikely to be dependent on confounded variables such as total body water.
• From this limited but consistent data, it can be tentatively concluded that BMI and body fat effects as they relate to these TDC measurements do not have a major impact.