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!