--- title: "Marathon Runners’ Bodies Appear to Be Devouring Brain Tissue, Scientists Say" description: "A new paper suggests that marathon runners' bodies might turn to the myelin sheath as a mid-race energy source." date: "2023-11-05" modified: "2023-11-05" authors: - name: "Maggie Harrison Dupré" job_title: "Senior Staff Writer" link: "https://futurism.com/authors/mharrison" url: "https://futurism.com/neoscope/marathon-runners-devouring-brain-tissue" categories: - "Brain" - "Health & Medicine" - "Neuroscience and Brain" tags: - "brain" - "brain health" - "exercise" - "health" --- # Marathon Runners’ Bodies Appear to Be Devouring Brain Tissue, Scientists Say ![A new paper suggests that marathon runners' bodies might turn to the myelin sheath as a mid-race energy source.]() *August 2005 \Image: Arctic-Images/Getty Images\* Talk about using your head. In a recent — though yet-to-be-peer-reviewed — [paper](), scientists posit that marathon runners' bodies might turn to brain tissue as a mid-race energy source, gobbling down the mind's protective myelin layer and turning it into fuel. Myelin is a fatty tissue found in our body's nervous system, coating our brain and nerve fibers in an extensive casing of insulating plasma known as the myelin sheath. And importantly, as Klaus-Armin Nave, a neurobiologist at Göttingen, Germany's Max Planck Institute for Multidisciplinary Sciences — who was not involved in the study — [told *Science News*](), it's long been "thought that myelin sheathes were assembled, inert structures of insulation that don't change much after they're made." In other words, they were widely thought to be unchanging structures with a single job to do. But according to the paper, published in early October as a preprint, before-and-after scans of a handful of marathon runners' brains tell a different story: that myelin is a dynamic and adaptable tissue that's not only available to the body as a reserve energy source during prolonged physical exercise, but also as a *replenishable* source of fuel to boot. The study itself is fairly simple. Led by Carlos Matute, a neurobiologist at the Achucarro Basque Center for Neuroscience at the Leioa, Spain-based University of the Basque Country, the scientists took images of four marathon runners' brains in the 48 hours leading up to, and in the 48 hours after, a big race. As it turns out, the before-and-after differences in myelin levels appear to be quite drastic, with the "after" scans showing stark declines in the insulating tissue — a finding that seems to support the hypothesis that the runners' bodies looked to their brains for an extra hit o' juice to get over the finish line. "This is definitely an intriguing observation," neuroimaging scientist at the National Institute on Aging in Baltimore Mustapha Bouhrara, who was not involved in the study, told *Science News* of the research. "It is quite plausible that myelin lipids are used as fuel in extended exercise." Perhaps most fascinating, however, is what appears to have happened in the brains of some of the runners in the weeks following the race. According to the study, when the researchers scanned two of the original four marathoners' heads two weeks after the 26.2-miler, they found that the runners' depleted myelin appeared to have bounced back in full, suggesting that the stuff is much more adaptable than previously thought. There are a few notable caveats to this research. Again, it's not peer-reviewed, and four people isn't a particularly large sample size. There's also a chance that the depletion seen in the scans is actually a case of dehydration — the channels between myelin's lipid bilayers are [packed with water]() — although the scientists involved in the study seem pretty staunch in their opinion that dehydration has nothing to do with the changes. "In our opinion, this is not the case," Matute told *New Science*, noting that the 48 hours between the race and the following scans would have given the runners enough time to rehydrate. Another sign that dehydration wasn't the culprit? Like a dried sponge, a dehydrated brain will shrink; the runners' scans, said Matute, showed nothing of the sort. "We saw that there is no shrinkage of the brain at all," the scientist told *New Science*. The paper is very preliminary, in other words, but its findings are thought-provoking, especially considering how little we actually know about our own brains. Hopefully this research warrants future research into the unlikely dynamism of the myelin sheath — and whether marathoners are the only folks who might be tapping into myelin as an energy source. **More on brains:** [*Research Suggests That Bad Dental Health May Increase Risk of Dementia*]() ## Author At Futurism, I've reported extensively on the rise of AI as a cultural and business force shaping the media industry, and more broadly how those dynamics are changing how we all consume and share information and relate to one another. I'm also fascinated by public health policy and ethics, the role of emerging tech in politics and governance — and the powerful people and forces at those intersections — climate change, and the environment. My investigation on Sports Illustrated's use of AI-generated authors with fictional biographies won a 2024 Mirror Award for "Best Story on Media Coverage of Artificial Intelligence in Journalism and the Media" from Syracuse University's SI Newhouse School, I contributed to Niemen Lab's 2025 Predictions for Journalism series, and I've discussed my work for Futurism during appearances on NPR, CNN, the BBC, the CBC, and more. I grew up in rural Pennsylvania and attended the University of Massachusetts Amherst, where I played Division I field hockey for the Minutewomen as a midfielder. Since then, I've lived in New Orleans, Louisiana and Manhattan, New York. I spend my free time running, reading, perusing archival fashion, and searching for the world’s best negroni. I also have a debonair tuxedo cat, Westley, who's named after "The Princess Bride." ### Author social links [Bluesky]()