Is bioimpedance analysis feasible in transgender men?

Background & aims

Accurate fat mass (FM) and muscle mass (MM) assessment is an informative marker of an individual's health. However, the optimal method for assessing body composition in transgender men remains to be determined. Here, we aim to compare body composition estimates in transgender men by bioimpedance analysis (BIA) using the reference settings for “males” and “females” and by dual x-ray absorptiometry (DXA) scans.

Methods

We conducted a cross-sectional pilot study investigating the body composition of 10 transgender men undergoing hormonal therapy using BIA and DXA scans.

Results

BIA yielded significantly different estimates of body composition depending on the use of either “female” or “male” settings (P<0.05). BIA underestimated FM independent of using the “male” or “female” setting compared to DXA estimates by -6.5% (95% CI -7.2; -5.8) and -5.4% (95%CI -6.8; -4.0), respectively. BIA tend to estimated a higher MM, especially for the trunk area [BIA (“female”) vs. DXA; 6.6kg (95% CI 5.3; 7.9), BIA (“male”) vs. DXA; 5.7kg (95% CI 4.9; 6.4)]. For FM the “female” setting came closest to the DXA scans for the extremities, although the “male” setting seemed more precise for the trunk region. Regarding MM, the BIA “male” setting best resembled the DXA scan estimates.

Conclusions

We observed a significant difference in body composition estimates when using BIA with either “female” or “male” settings in transgender men. In general, BIA tend to estimate lower FM and higher MM compared to DXA. Therefore, we encourage caution when interpreting body composition estimates in transgender persons.

Registered at www.clinicaltrials.gov/ (study ID: NCT05728853).