Physical Fitness and Body Composition in Transgender vs. Cisgender Individuals: A Systematic Review and Meta-Analysis

ObjectiveTo compare fitness and body composition between transgender and cisgender individuals. DesignSystematic review and meta-analysis. Data sourcesPubMed, Web of Science, Embase, and SportDiscus databases were searched in June 2024, supplemented by manual citation reviews. Eligibility criteriaInclusion criteria comprised studies of transgender individuals comparing physical fitness/body composition pre-to-post gender-affirming hormone therapy (GAHT) or vs. cisgender controls, with quantitative outcomes reported. ResultsFifty-one studies (6,434 participants) were analyzed. Transgender women (TW) exhibited comparable fat mass to cisgender women (CW), but higher than cisgender men (CM). TW showed greater lean mass than CW, but lower than CM. Upper- and lower-body strength were similar between TW and CW, but lower than CM. TW and CW had similar VO2 peak, but TW exhibited lower values than CM. Transgender men (TM) exhibited similar fat mass to CW, but higher than CM. TM showed higher lean mass than CW, but lower than CM. Upper-body strength was higher in TM than CW, but lower than CM. GAHT in TW increased fat mass, reduced lean mass and upper-body strength, with no differences in lower-body strength over 1-3 years. TM demonstrated reduced fat mass and increased lean mass, upper- and lower-body strength post-GAHT. Risk of bias was moderate for most studies, with limited observations for specific outcomes (e.g., VO2 peak). ConclusionWhile TW exhibited higher lean mass than CW, their physical fitness was comparable. Current evidence is limited but does not justify blanket bans based on assumptions of inherent athletic advantages for TW over CW. WHAT IS ALREADY KNOWN ON THIS TOPICO_LIThe inclusion of transgender women in female sports categories remains a highly contentious subject. C_LIO_LIExisting studies suggest that gender-affirming hormone therapy (GAHT) alters body composition in transgender individuals, but evidence on functional performance outcomes (e.g., strength, endurance) remains inconsistent. C_LIO_LIPolicies advocating blanket bans on transgender women (TW) in female sports often cite residual advantages from prior testosterone exposure, despite limited empirical support for sustained performance disparities post-GAHT. C_LI WHAT THIS STUDY ADDS?O_LIThis systematic review and meta-analysis synthesizes data from 51 studies (6,434 participants), demonstrating that, while TW showed higher absolute lean mass than cisgender women (CW), there are no significant differences in upper/lower-body strength or VO{square}peak after 1-3 years of GAHT. C_LIO_LIThese findings challenge the validity of blanket bans predicated on assumptions of inherent athletic superiority of TW over CW. C_LIO_LITransgender men (TM) exhibit body composition and strength metrics intermediate between CW and cisgender men (CM) post-GAHT. C_LIO_LICritical research gaps are identified, including a lack of long-term GAHT data, underrepresentation of transgender athletes, and inconsistent controls for confounders (e.g., training history, puberty blocking). Future studies must prioritize sport-specific performance metrics and longitudinal designs to inform equitable policies. C_LI