Home Science Biology Fallon Fox & Ronda Rousey Could Have The Same Bone Density

Fallon Fox & Ronda Rousey Could Have The Same Bone Density


There has been a lot of talk about the transgendered fighter Fallon Fox, who was born a man but has since had gender reassignment surgery (removing the male genitalia and surgically creating a visually similar female genitalia) and whether she should be able to compete against other women that we’ve covered in recent posts.

UFC President Dana White has given his opinion on the matter and in a previous article saying that he’ll “leave it up to the professionals and let them decide.” We had a sit down with Doctor Samuel O. Mayeda, M.D., F.A.C.E., F.A.C.P. of The Endocrine Medical Group, Inc. in Orange, Ca regarding the issue.

Many women in MMA are reluctant to go into the ring with her. If you watch Fox’s last fight you can tell the power she has behind those fists may seem to others as a physical strength that no woman (in the same weight class) could ever truly have. In addition to the surgery a transgendered individual must permanently maintain their bodies by applying exogenous estrogen.

Ronda Rousey, UFC’s bantamweight champ, has been asked if she would ever fight her. She brings up an argument that there is a difference in bone density from Fox’s development as a man, prior to surgery, that would cause the bout to be unfair and consequently dangerous for the ‘natural’ female.

At first glance it seems to be a logical and valid argument.  However, we were curious to know what the actual science of the matter is. In taking a closer look at this scenario we asked Dr. Samuel O. Mayeda for his thoughts on the matter.

Dr. Mayeda had this to say about the bone density concerns being expressed, “Well there is so much variability between humans, for example there are people, women who have bigger bones than I have, just because I’m a male it doesn’t mean that there might be a disadvantage.”

When we suggested the possibility of bone mass being affected by the lack of testosterone in Fox’s body since the surgery six years ago, Dr. Mayeda said that it “wouldn’t necessarily result in a change in bone mass because she was receiving estrogen, which also preserves bone mass.”

Although the bone mass may be that of the male Fallon Fox, Dr. Mayeda doesn’t believe this should be a reason to exclude her from fighting other women. Everyone has different bone mass and length. Dr. Mayeda went on to say, “There are many women who are stronger then I am for my weight and height.” So how do we tackle the issue of bone density variations between males and females? Dr. Mayeda advised that if one were curious they could perform a bone density test.

density test

The dual energy X-ray absorptiometry (DEXA) procedure can measure as little as a 3 percent variance in bone density of an individual. It is used to estimate bone density in your spine and hip. This test is performed by aiming two different energy source beams at the individual’s bones as they lay on an examination table. The measurement of bone mass is determined through comparison of light beam amounts blocked by the bone and soft tissue. The stronger, or more dense bone allows fewer X-ray beams to pass through, and less dense bones permit more of the X-ray beams to pass through. Women often get this done every 2 years, as advised by their medical practitioners. So Rousey could have her medical records referenced and then compared with results of a bone density test from Fallon Fox, then we could see exactly what the true variance and advantage may be for either fighter. The results of such an examination could rule out Rousey’s argument of Fox’s bone denisty being an issue with fighting women.


If the tests do come back with Fox being off the charts compared to other female fighters, then there could be a valid scientific argument against allowing Fallon Fox to fight women. However wether this should be a blanket rule for all transgendered individuals would require quite a bit more data.

Dr. Mayeda did offer a quick solution to identifying how much of a bone density advantage Fallon Fox might have.  Since there is plenty of data from the many DEXA exams performed on women of various ages you could compare Fox’s results with that of the standard medians.  This would give a quick answer to whether Fallon Fox is far outside the average female bone density. Many may not know these statistics but Fallon Fox is only 5’7 and 144 lbs, Dr. Mayeda called her “petite” jokingly. He explained that the same test for comparison to women using the DEXA could be performed for men as well.  Thus we could clearly see just where Fallon Fox sits in the averages of both.

Supposing the test were to be performed on fighters like Rousey and Fox for comparison.  What would we find?  Would you be surprised to learn that Rousey could possibly have stronger bone density than that of a similar average man in the same weight class?  Where do the lines for fairness in the sport get drawn and why?  If Rousey were to have denser bones than that of most women and many men, then should she be relegated to only fighting in male bouts?  This would be the same logic applied for the same principle.  However, if not for bone density, then what is the prejudice being expressed by both male and female fighters alike when it comes to Fallon Fox?

Let us know your thoughts in the comments!

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  • Still think they should let
    mitrione fight fox.lol

    • Evan Stoumbelis

      Lol, that’d be a solution to the Mitrione problem. But I still maintain that Fox has an advantage, not just bone density.

      • Hey Evan, you know I respect your opinion. So I’m curious to know what other advantages she might have. To be totally fair and transparent, the amount of statistical data on Transgendered individuals is way too limited to say across the board things should or should not be allowed. Obviously being cautious and conservative the likely prudent move would be to say “it should not” be allowed. However if we can break it down and really see what makes things work, you know we love doing that here! 🙂

        • Evan Stoumbelis

          Of course man, men and women’s brains are wired differently. Scientists found that men have more synapses which is where impulses are passed through, however according to them this doesn’t necessarily give men a huge advantage, but where it does help, is spatial perception. This would give Fallon Fox an advantage at judging distance before throwing a strike, shooting for a takedown, or feinting away.

          • That is really a very interesting point. (Just a clarification, total synapses of males are not necessarily greater than women but there are certain regions that each sex has more development in than the other. i.e. social centers in the female brain) It is true that males have a better developed sense of spacial perception (at least historically they have). This aided in the role of hunting and fending off predators or other threats early on in our history. Let’s take this thought one step further though, citing the differences in brain development between males and females. Do you think it is possible that by some genetic mutation that a transgendered person might have a brain that developed similarly to that of a woman and yet the rest of their physical attributes appear male? (If you do some research you will find very interesting data on certain hermaphroditic individuals who later in life chose gender based on their psychological temperament. They are born with both male and female genitalia but then are allowed to chose a role final role before puberty. It’s fairly rare and I cannot cite references from the top of my head, though usually the parents make the decision for the child just after birth. What if they chose incorrectly? What a quandary that would be!) 🙂

          • rrosettastone

            Don’t know, on those points Luca. What I do know is physiologicical. Fallon Fox’s body went thru male puberty. My body went thru female puberty, as did my daughter’s. My son, of course went thru male puberty as did both of my ex husbands & my brother. Big difference. The physical result in the body is really extreme. I’m sure you’ve noticed that. Get it?

          • rrosettastone

            in sports, it’s not really the brain that matters have you noticed?

          • Many athletes would disagree. 😉 However I believe I may know where you were trying to go with that statement.

          • I say the brain matters more than anything in technical sports like mma. Of course you need to be quite durable as well. I’ve never seen an intellectually subpar person excel in sports that require that rapid decision making that’s required in a diverse sport

          • Evan Stoumbelis

            I couldn’t disagree more, like Joshua below said, the brain is such an important factor in sports, especially in your reaction time. Decision making is a huge part of sports and the brain plays a major role in that.

          • Evan Stoumbelis

            Also as an example people with ADHD and ADD have faster reaction times. This comes from a brain difference, which would back up the statement that the brain is arguably the biggest factor.

          • Yes all true and that’s why we went to a reputable physician to get some insight. The responses are in the article. If there are any physicians reading this that would like to offer their opinion we would be very happy to have that. Our position is neutral, we just want to understand the science.

          • Evan Stoumbelis

            There was actually a Nova special on this! When the parents decide the gender and the child goes through gender reassignment surgery and the parents raise them that gender. In the Nova special the guy grew up a girl and knew something was wrong and decided to have gender reassignment surgery AGAIN to go back to a male, and he lived out the rest of his life as a man, having a wife, and kids.

          • Now this is really interesting. I had not seen this program. By chance do you happen to know when it aired? Thanks Evan!

          • Incidentally since this subject and your position on it has really piqued my interest I am going to do some more research. Perhaps this deserves a closer look…. although it is certainly veering away from the topic of MMA. What do you think Evan, does this subject warrant another article or should we just leave it for now? 🙂

          • Evan Stoumbelis

            If you’re up for the research I’d definitely enjoy reading more in another article!

          • Awesome, then we shall do it! 🙂

    • Amusing as it is I doubt it will happen lol

    • rrosettastone

      i’d love to see her beat the crap out of him.

  • rrosettastone

    Gay rights don’t trump women’s rights. Get “her” out of the women’s ring. Don’t let “transgendered” steal the women’s sport.

    • Alex Briggs

      Gay and Transgender are two entirely different things. Being transgender does not imply a specific sexual orientation. It is a matter of someone’s gender identity not matching their actual gender. I feel if you are going to debate about women’s rights and equality to men it should only solidify the notion that Fallon Fox should be allowed to fight women.

      • You know one of the most confusing aspects of of Gay/Lesbian and Transgendered is that they are often lumped into the same category. It may be an old psychological or psychiatric concept of categorization, I am not sure. I agree with your assessment that they certainly appear to be different, however there are also similarities in that they are often equally disenfranchised, criticized or dismissed for similar psychological reasons. It’s natural for many individuals to assume that while 1+2=3 and 5-2=3 even though fundamentally the nature of the equations differs the result is the same (by perception).

        • rrosettastone

          There should be, as in India, the 3rd gender, let those undefined compete against eachother. But to require that women fall under the same catagory as fallon fox is to strip women of what i have fought my whole life for. That’s not fair. If Fallon Fox wins this thing and is allowed to compete as female after all I’ve worked for, I’ve got nothing for my sport, I’m too old for any major trophy, I just want the young real women to have a shot at it.

          • To be perfectly honest Ellen I have to say I see your point and your make a valid argument here. There must be other women who feel similarly. Thus should there be a Transgendered ‘league’? It’s certainly a question worth asking.

          • Evan Stoumbelis

            Like Chael Sonnen said, add in a new league for juicers, let all the roid freaks fight in their own league. Do the same with transgenders.

        • Evan Stoumbelis

          Agreed, Also one of the reasons it’s such a hard topic is because it’s all uncharted territory, this is all grey area, there is no definitive answer yet.

      • rrosettastone

        genetics is a single thing. p

        • rrosettastone

          It’s not genetics as much as it is physiology.

          • Genetics dictate your physiology Ellen. Your position on the matter is noted. If you have anything new to contribute to the conversation (that isn’t just an insult or callous remark) then please feel free. Otherwise please do not saturate the conversation with repetitive rhetoric.

      • rrosettastone

        i don’t think “she” should be allowed to fight women. I believe “she” has too much left of the male body. Alex, if you are physiologically male & have any real experience with women, you should realize this.

        • Evan Stoumbelis

          Don’t get me wrong I don’t think Fallon Fox should be allowed to fight women…however in fairness scientists have said after 6 years of taking the female hormones hher muscles would be equal to that of a woman

    • Hi Ellen,

      Just a case in point, no single group of individuals rights should trump any other group of individual’s rights. Most democracies were founded on a principle of fairness before equality. If you will note, throughout history many individuals have lost limbs, and were allowed to compete in a sport so long as they had sufficient safety and support to do so. That all being said, we’d like to try and focus on what makes this unfair “Scientifically”. We know where many people stand on this from a matter of personal preference but preference doesn’t dictate fairness or equality. We’d be genuinely curious to know your thoughts on how this affects fairness and with the utmost respect (understanding the sensitivity of the issue) please let’s try and keep social politics out of the conversation. Thanks again for your viewership and participation in the community!

      Best Regards,
      Luca Rajabi
      President of SciFighting, LLC.

      • rrosettastone

        So Fallon Fox may have a “fragile” bone density, but where do we draw the line? We let him compete with women because he sure as hell can’t compete against men, but which transgender actually does cross the line? Tell me that? I cannot tell by your name, Luca, whether you are male or female. You have no doubt as to my gender. I’m about 30 yrs too old to compete and that long ago us ladies didn’t get to anyway. Fallon Fox should be fighting for a 3rd gender, shouldn’t be fighting to steal the women’s class.

        • rrosettastone

          Are you understanding me? I grew up in a world where I couldn’t do that & some wimp ass boy decides he’s a girl pays doctor for a trim job & then he can go steal my daughter’s trophy. Get it?

          • rrosettastone

            okay, so both my kids are a bit more cerebral than me, they’re not much into any sport. But I do have children around me that are. The boys are all they can be, the girls are incredibly all they can be. I’m not bitter over what I couldn’t get back in the day when women were not trained, I’m terrified, however of what happens when it becomes more important to insure that the transgendered get their spot than to let the young woman bask in their glory.

          • rrosettastone

            where is the joy of the women’s sport when the “transgendered” (and it will be bigger men than that) when they steal it from the women?

          • I cannot answer that question, but I would be rather surprised to see a sudden flood of transgendered individuals rushing into the ring! 🙂 Statistically speaking if that many men are willing to undergo surgery and then compete in mixed martial arts, then we have larger challenges to overcome as a species 🙂

          • Alex Briggs

            The point you try to make about transgendered individuals “stealing” anything from women is absurd. The amount of time, effort, sacrifice, and dedication put forth by any fighter, regardless of gender points to no other conclusion than they have EARNED their chance to compete. And Fallon Fox has not only identified herself as a woman but has done everything correctly to classify her has such. But, maybe, we are all asking the wrong question. Maybe we should be asking “when”. Because this will most likely happen sometime in the near future.

          • Ellen, your argument is clear. SciFighting is about supporting diversity in the sport. The right for women to compete is paramount to ensuring diversity. Yet before we exclude someone else from the sport we also need to have very good reasons. Your choice language is quite frankly rather inflammatory. Please put yourself in the shoes you’ve worn your entire life. What did “MEN” say about women 50 years ago? What would they have said at the notion of a woman even competing in the same “type” of sport? You better than anyone I’m sure can understand how sensitive this is for everyone involved.

        • To address your comment on my “name”. It is the Italian form of the name you may know as “Luke”. It is a name that dates back thousands of years, its origin being that of identifying a “man from Lucania” (an ancient district of southern Italy). Thus you may safely conclude that I am a male although my gender as it relates to this conversation is irrelevant. I am however the president of SciFighting and my biography is posted on this site in the “Who’s A Part Of Scifighting?” section.

          I understand these are sensitive topics and I would be the last person to claim to have a definitive answer on whether Fallon Fox should be allowed to fight men or women. The facts are that the science is too sparse on this subject to give a clear answer. Time will tell.

          The only precedent for something like this was in Thai Land where, as you mention in your previous comment, Transgendered individuals are considered a third gender. There was an individual by the name of Nang Thoom who changed from Male to Female and continued to compete in Muay Thai but fought men even after the sex change.

          I do not know the logic or reasoning behind Fallon Fox’s choices but it raises an incredibly interesting predicament.

          My position is such that I believe that Women should be allowed to perform the same activities as men without any prejudice or favoritism. That would be fair. Allow them and their bodies to decide what they can and can’t do, not a panel of judges.

          That all being said, the social allegories are too intense to ignore… the concept of a man beating on a woman is one that is socially unacceptable on many many levels. That so many still perceive Fallon Fox as a man rather than a woman makes for a very difficult transition for many to make when going towards acceptance of her desires.

          What if none of us had ever known? Would we question it? What are the lines between the capabilities of men and women? We are just scratching the surface of these matters, yet I believe it is important to discuss as not only is it relevant to the sport but also to the perception of women and men alike.

  • rrosettastone

    Stuff it Fallon Fox. You don’t have the tools to go up against a man & you don’t have the experience to be a woman. Look around & get yourself a life. I’m 57, I was born female grew female, missed out on athletics because my generation didn’t recognize female sports. Go cry in your green tea. Go work for the purpose of the 3rd Gender. Get out of women’s sports because you are not us. And you cannot be, science just does not go that far.

    • This site is not affiliated with Fallon Fox in any way. If you have statements you wish to make to her then do so directly through a medium she owns. You are being warned. This site will not be used as a platform for personal attack.