Accuracy of Anthropometric Equations in Estimating Body Fat Percentage in Transgender Men Undergoing Gender-Affirming Hormone Therapy

Transgender people may opt for the use of sex steroids and, in some cases, hormone blockers, which can lead to changes in body fat distribution. The aim of this study was to verify the accuracy of anthropometric equations to estimate the body density (BD) of transgender men who are undergoing Gender-Affirming Hormone Therapy (GAHT). Four transgender men (25-32 years old), who had performed GAHT for at least six months and used the hormone testosterone cypionate participated in the study. The reference criteria for BD was air displacement plethysmography (ADP). In addition, BD was estimated using anthropometric equations for both male and female sexes (Durnin & Womersley, 1974; Jackson & Pollock 1980; Lohman, 1981). The body fat percentage (%BF) was estimated by the Siri equation. For two participants (Cases 1 and 3), the equations for males underestimated the %BF, while only for Case 3 the equation for both sexes underestimated the %BF. For the other two participants (Cases 2 and 4), all equations overestimated the %BF. Of note, one participant undergoing GAHT for six months showed a %BF assessed by ADP like values obtained using equations for cisgender women, while those with longer time on GAHT presented similar %BF obtained by ADP to obtained by equations developed for cisgender men. In conclusion, the results of this study indicate the need to develop specific anthropometric equations for the transgender population. In addition, the time on GAHT of the transgender person seems to be a critical factor.