Body composition and physical fitness in transgender versus cisgender individuals: a systematic review with meta-analysis.

Transgender women had similar relative fat mass compared to cisgender women after gender-affirming hormone therapy.

• SMD -0.33, 95% CI -0.72 to 0.05
• GRADE certainty: very low
• 52 studies with n=6485 participants were included in the overall review
• Comparison was made versus cisgender women controls

Transgender women had similar relative lean mass compared to cisgender women.

• SMD 0.19, 95% CI -0.14 to 0.53
• GRADE certainty: low
• Despite higher lean mass than cisgender women overall, the difference was not statistically significant

Transgender women had similar upper-body strength compared to cisgender women.

• SMD 0.54, 95% CI -0.95 to 2.02
• GRADE certainty: very low
• Wide confidence intervals indicate substantial uncertainty in this estimate

Transgender women had similar lower-body strength compared to cisgender women.

• SMD 0.05, 95% CI -1.31 to 1.40
• GRADE certainty: very low
• Confidence interval was very wide, reflecting high heterogeneity

Transgender women had similar maximal oxygen consumption compared to cisgender women.

• SMD -0.28, 95% CI -0.81 to 0.25
• GRADE certainty: very low
• Physical fitness as measured by VO2max was not significantly different from cisgender women

Transgender men exhibited higher relative fat mass than cisgender men.

• SMD 0.96, 95% CI 0.28 to 1.64
• GRADE certainty: moderate
• This was a statistically significant difference favoring higher fat mass in transgender men compared to cisgender men

Transgender men exhibited lower relative lean mass than cisgender men.

• SMD -6.42, 95% CI -12.26 to -0.58
• GRADE certainty: moderate
• The very large SMD and wide confidence interval suggest high heterogeneity across studies

Transgender men exhibited lower upper-body strength than cisgender men.

• SMD -1.46, 95% CI -2.52 to -0.40
• GRADE certainty: moderate
• This was a statistically significant difference indicating lower upper-body strength in transgender men versus cisgender men

In transgender women, gender-affirming hormone therapy (GAHT) was associated with increased fat mass and reduced lean mass and upper-body strength over 1–3 years.

• Changes were observed in pre-to-post GAHT comparisons within transgender women
• The duration of GAHT examined was 1–3 years
• Despite these changes, physical fitness remained comparable to cisgender women

In transgender men, gender-affirming hormone therapy was associated with reduced fat mass and increased lean mass and strength.

• Pre-to-post GAHT comparisons showed favorable changes in body composition for transgender men
• Strength also increased following GAHT in transgender men
• Despite these improvements, transgender men still had higher fat mass, lower lean mass, and lower upper-body strength than cisgender men

The overall certainty of evidence across included studies was mostly low, with heterogeneous quality.

• GRADE ratings ranged from very low to moderate across outcomes
• 52 studies (n=6485) were included from PubMed, Web of Science, Embase, and SportDiscus
• The review was pre-registered: CRD42024562210
• Inclusion criteria comprised studies comparing body composition or physical fitness pre-to-post GAHT or versus cisgender controls