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Michael Searles
Deputy Health Editor
04 February 2026 6:53am GMT
Trans athletes who were born male have no advantage over women, a British Medical Journal (BMJ) study has claimed.
The researchers argued that there was no evidence “to justify blanket bans” on trans women taking part in women’s sport.
The team looked at the strength, fitness and body composition of transgender people taking cross-sex hormones compared with women and men not taking drugs.
Authors of the study, which was published in BMJ Group-owned British Journal of Sports Medicine, said its findings challenged “assumptions” that trans women had an inherent advantage in sport.
The 2024 Olympic Games in Paris were engulfed by controversy when Algeria’s Imane Khelif won the women’s welterweight boxing gold medal despite being disqualified from the 2023 World Championships for reportedly failing a gender eligibility test.
The new research has attempted to cast doubt on whether an apparent sporting advantage stacks up.
The report has prompted criticism from academics and sex-based rights campaigners for flaws in how it was conducted.
The authors from the University of São Paulo in Brazil have also admitted that there are gaps in the “imperfect evidence” that they used to come to these conclusions.
Multiple sporting bodies in the UK banned trans women from taking part in women’s sport last year after the Supreme Court ruled that the legal definition of a woman under the Equality Act is based on biological sex.
This included football and cricket, while other sports such as cycling and triathlon had already introduced an open category for trans athletes.
The International Olympic Committee is looking at a trans ban, which was a pledge made by Kirsty Coventry, its president, in her election campaign.
The scientists analysed 52 studies on 6,485 people, the majority of whom were transgender.
They found that trans women had more lean mass, a proxy for muscle, but no observable differences from other women in body strength or maximal oxygen consumption – a key measure of cardiorespiratory fitness.
These metrics were also much lower than other men because of cross-sex hormones, which block testosterone production, the research said.
The authors admitted that the evidence was of mixed quality and lacked a range of ages, sports and competitive levels.
However, they said that it did not back up the “prevailing theories” of an inherent advantage or “justify blanket bans” in sport.
“Ideally, to resolve speculation, future longitudinal studies should prioritise performance-specific metrics in transgender athletes,” they said.
“However, one should be aware of the scarce number of transgender athletes, particularly in the elite sport.”
Commenting on the study, Alun Williams, a professor of sport and exercise genomics at Manchester Metropolitan University, said the research “suffers from several problems”, including that fitness levels were not tracked over time and before treatment began.
He said the strength tests relied on “voluntary effort” and so should be “treated sceptically”, especially as the trans women had more muscle mass, while it was “almost worthless to compare groups without tight assessment of training history”.
Prof Williams added that he and other experts had “reviewed the same literature” and found that the loss of sports performance among trans women on hormones was “notably smaller than typical differences between men and women”.
Fiona McAnena, the director of campaigns at sex-based rights charity Sex Matters, said: “Men do not shrink or magically lose all their male advantages when they identify as women, no matter what hormones they take.
“Everyone knows no one can change sex, and no academic analysis or statistical data tricks can prove that men should be allowed to compete in women’s sport based on a claimed female identity,” she said.
“The males in this study may have hobbled their own athletic prowess voluntarily by suppressing their testosterone, but that is not an argument for forcing female athletes to compete with them.”
Dr Blair Hamilton, research associate in applied sport and exercise physiology at Manchester Metropolitan University, said the study highlighted that “you can’t assume that having slightly more muscle automatically means having better sporting performance”.
He added that to know how something affects elite athletes, “you really need elite athletes to study, and at the moment, there are very few openly transgender elite athletes anywhere in the world”.
Trans athletes have no advantage over women, study claims
Researchers argue there is no evidence to justify a blanket ban on transgender athletes competing against womenMichael Searles
Deputy Health Editor
04 February 2026 6:53am GMT
Trans athletes who were born male have no advantage over women, a British Medical Journal (BMJ) study has claimed.
The researchers argued that there was no evidence “to justify blanket bans” on trans women taking part in women’s sport.
The team looked at the strength, fitness and body composition of transgender people taking cross-sex hormones compared with women and men not taking drugs.
Authors of the study, which was published in BMJ Group-owned British Journal of Sports Medicine, said its findings challenged “assumptions” that trans women had an inherent advantage in sport.
The 2024 Olympic Games in Paris were engulfed by controversy when Algeria’s Imane Khelif won the women’s welterweight boxing gold medal despite being disqualified from the 2023 World Championships for reportedly failing a gender eligibility test.
The new research has attempted to cast doubt on whether an apparent sporting advantage stacks up.
The report has prompted criticism from academics and sex-based rights campaigners for flaws in how it was conducted.
The authors from the University of São Paulo in Brazil have also admitted that there are gaps in the “imperfect evidence” that they used to come to these conclusions.
Multiple sporting bodies in the UK banned trans women from taking part in women’s sport last year after the Supreme Court ruled that the legal definition of a woman under the Equality Act is based on biological sex.
This included football and cricket, while other sports such as cycling and triathlon had already introduced an open category for trans athletes.
The International Olympic Committee is looking at a trans ban, which was a pledge made by Kirsty Coventry, its president, in her election campaign.
The scientists analysed 52 studies on 6,485 people, the majority of whom were transgender.
They found that trans women had more lean mass, a proxy for muscle, but no observable differences from other women in body strength or maximal oxygen consumption – a key measure of cardiorespiratory fitness.
These metrics were also much lower than other men because of cross-sex hormones, which block testosterone production, the research said.
The authors admitted that the evidence was of mixed quality and lacked a range of ages, sports and competitive levels.
However, they said that it did not back up the “prevailing theories” of an inherent advantage or “justify blanket bans” in sport.
“Ideally, to resolve speculation, future longitudinal studies should prioritise performance-specific metrics in transgender athletes,” they said.
“However, one should be aware of the scarce number of transgender athletes, particularly in the elite sport.”
Commenting on the study, Alun Williams, a professor of sport and exercise genomics at Manchester Metropolitan University, said the research “suffers from several problems”, including that fitness levels were not tracked over time and before treatment began.
He said the strength tests relied on “voluntary effort” and so should be “treated sceptically”, especially as the trans women had more muscle mass, while it was “almost worthless to compare groups without tight assessment of training history”.
Loss of performance
He argued it could be that, as a group, they “were not as strong or as aerobically fit” as other men before transitioning, and pointed out that trans women still had physical advantages such as height and limb length, compared with those born female.Prof Williams added that he and other experts had “reviewed the same literature” and found that the loss of sports performance among trans women on hormones was “notably smaller than typical differences between men and women”.
Fiona McAnena, the director of campaigns at sex-based rights charity Sex Matters, said: “Men do not shrink or magically lose all their male advantages when they identify as women, no matter what hormones they take.
“Everyone knows no one can change sex, and no academic analysis or statistical data tricks can prove that men should be allowed to compete in women’s sport based on a claimed female identity,” she said.
“The males in this study may have hobbled their own athletic prowess voluntarily by suppressing their testosterone, but that is not an argument for forcing female athletes to compete with them.”
Dr Blair Hamilton, research associate in applied sport and exercise physiology at Manchester Metropolitan University, said the study highlighted that “you can’t assume that having slightly more muscle automatically means having better sporting performance”.
He added that to know how something affects elite athletes, “you really need elite athletes to study, and at the moment, there are very few openly transgender elite athletes anywhere in the world”.
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