Trans Athletes in Sports: What the Data Really Shows

A heated debate has erupted over trans women playing in top‑level women’s sports. It started after a guard from the Indiana Fever told ESPN she wants to keep young girls safe from competing against biological men. The comment sparked a wave of political talk, protests and TV chatter that seems more about division than support. Soon after, two former NBA players said they would enter the 2027 WNBA draft, claiming they now identify as women. The WNBA task force met, called the move a bad‑faith attempt to mock or sideline people, and issued a clear statement against such tactics.

Despite the noise, the actual number of trans athletes in college sports is tiny. In 2024 the NCAA president said fewer than ten out of over half a million student‑athletes are trans, which is less than two thousandths of a percent. No openly trans woman has ever played in the WNBA during its thirty‑year history. In response, former President Trump signed an order that blocks trans athletes from girls’ and women’s teams and threatens to cut federal funds from schools that ignore it. The NCAA then said it would limit women’s sports to those assigned female at birth. The International Olympic Committee added a rule for the 2028 Los Angeles Games that only allows biological females, based on a one‑time SRY gene test.

Amid the shouting, Kirsti Miller, a trans athlete and researcher from Australia, asks for a conversation grounded in science rather than rhetoric. She notes that Australian sporting groups have had policies for about twenty years that require trans women to undergo hormone therapy to lower testosterone and keep those levels steady while competing. Miller herself was a multi‑sport star, including a champion swimmer on the men’s circuit, before she transitioned. She began hormone treatment in 1999 and in 2013 became the first trans woman to play in the women’s division of the Australian Football League. Now retired, she uses her experience to push for research.

Miller points to a 2023 study she co‑authored in the Journal of Clinical Endocrinology & Metabolism. The research found that after a year of gender‑affirming hormone therapy, trans women gained roughly thirty percent more fat mass, lost about nine percent of muscle mass, and saw drops in bone mineral density and strength. She explains that within three months the therapy reduces oxygen delivery to the heart and limbs, slows recovery, and makes endurance performance worse than that of cisgender women. In short, the data suggest that hormone‑treated trans women do not have an advantage; they often perform less well in long‑lasting events.