Change in Visceral Fat and Total Body Fat and the Effect on Cardiometabolic Risk Factors During Transgender Hormone Therapy

Abstract

Introduction: Excess visceral fat increases the risk of type 2 diabetes and cardiovascular disease and is influenced by sex hormones. Our aim was to investigate changes in visceral fat and the ratio of visceral fat to total body fat (VAT/TBF) and their associations with changes in lipids and insulin resistance after 1 year of hormone therapy in trans persons.

Methods: In 179 trans women and 162 trans men, changes in total body and visceral fat estimated with dual-energy X-ray absorptiometry before and after 1 year of hormone therapy were related to lipids and insulin resistance [homeostatic model assessment of insulin resistance (HOMA-IR)] with linear regression analysis.

Results: In trans women, total body fat increased by 4.0 kg (95% CI 3.4, 4.7), while the amount of visceral fat did not change (-2 grams; 95% CI -15, 11), albeit with a large range from -318 to 281, resulting in a decrease in the VAT/TBF ratio of 17% (95% CI 15, 19). In trans men, total body fat decreased with 2.8 kg (95% CI 2.2, 3.5), while the amount of visceral fat did not change (3 g; 95% CI -10, 16; range -372, 311), increasing the VAT/TBF ratio by 14% (95% CI 10, 17). In both groups, VAT/TBF was not associated with changes in blood lipids or HOMA-IR.

Conclusions: Hormone therapy in trans women and trans men resulted in changes in VAT/TBF, mainly due to changes in total body fat and were unrelated to changes in cardiometabolic risk factors, which suggests that any unfavorable cardiometabolic effects of hormone therapy are not mediated by changes in visceral fat or VAT/TBF.

Keywords: hormone therapy; insulin resistance; lipids; transgender; visceral fat.

Figure 1.

Relative changes in measures of body fat distribution and body composition during 1 year of hormone therapy in 179 trans women and 162 trans men. Trans women: visceral adipose tissue: −1% (95% CI −4, 3); total body fat 21% (95% CI 18, 25); VAT/TBF: −17% (95% CI −19, −15); and lean body mass: −3% (95% CI −4, −2). Trans men: visceral adipose tissue: 1% (95% CI −4, 6); total body fat: −11% (95% CI −13, −8); VAT/TBF: 14% (95% CI 10, 17); and lean body mass 10% (95% CI 9, 11). Abbreviation: VAT/TBF, visceral adipose tissue/total body fat ratio.

Figure 2.

Change in VAT/TBF per BMI category in trans women and trans men during 1 year of hormone therapy. Trans women: relative change in VAT/TBF: BMI < 25 kg/m²: −17% (95% CI −21, −14); BMI 25-30 kg/m²: −16% (95% CI −22, −1); and BMI > 30 kg/m²: −15% (95% CI −23, −9). Trans men: relative change in VAT/TBF: BMI < 25 kg/m²: 15% (95% CI −10, −18); BMI 25-30 kg/m²: 6% (95% CI 11, 16); and BMI > 30 kg/m²: 15% (95% CI 9, 19). Abbreviation: BMI, body mass index; VAT/TBF, visceral adipose tissue/total body fat ratio.

Figure 3.

Associations between the change in VAT/TBF and change in cardiometabolic risk factors during 1 year of hormone therapy in 179 trans women and 162 trans men. Eight trans women and 6 trans men were excluded from the analysis on HOMA-IR for having diabetes mellitus. Abbreviations: HDL, high-density lipoprotein-cholesterol; HOMA-IR, homeostatic model assessment of insulin resistance; LDL, low-density lipoprotein cholesterol; TC, total cholesterol; TG, triglycerides; VAT/TBF, visceral adipose tissue/total body fat ratio.