Transgender vs Cisgender Body Composition and Fitness: What the Evidence Shows

What Does the New BJSM Meta-Analysis Reveal About Transgender Fitness?

The systematic review published in the British Journal of Sports Medicine pooled data from studies measuring body composition and physical fitness outcomes in transgender individuals receiving gender-affirming hormone therapy, comparing them with cisgender reference groups. Outcomes examined include lean body mass, fat mass, muscular strength, and cardiorespiratory capacity measured through standardized tests such as VO2max assessments.

Evidence suggests that testosterone therapy in transgender men leads to measurable increases in lean mass and strength over 12 months, while estrogen therapy combined with androgen suppression in transgender women reduces lean mass and strength, though not always to cisgender female baselines within the first year. The magnitude and timeline of these changes remain central to clinical and sports-governance discussions.

How Should Clinicians and Sports Bodies Interpret These Findings?

For clinicians, the review underscores the need to monitor cardiovascular fitness, bone density, and metabolic markers during gender-affirming care, since body composition shifts interact with long-term cardiometabolic risk. Organizations including the Endocrine Society and World Professional Association for Transgender Health (WPATH) emphasize individualized monitoring protocols during hormone therapy.

For sports governing bodies, the meta-analysis contributes to an ongoing evidence base used by organizations such as the International Olympic Committee and individual federations to shape eligibility criteria. The authors typically note remaining gaps — small sample sizes, short follow-up, and underrepresentation of elite athletes — meaning policies should evolve as higher-quality longitudinal data emerges.

What Are the Limitations and Gaps in Current Research?

The authors of such reviews consistently highlight methodological limitations: heterogeneous hormone regimens, varying baseline fitness levels, limited follow-up beyond two to three years, and inconsistent outcome measurement across studies. Few studies enroll competitive or elite-level athletes, making direct extrapolation to professional sport contexts difficult.

Additional research priorities include longer follow-up periods, standardized measurement protocols, inclusion of non-binary participants, and studies examining functional performance metrics beyond strength and aerobic capacity. The BJSM publication is part of a growing literature base aiming to replace speculation with empirical data in this clinically and socially complex area.