Jjazz
#1
Running a marathon might temporarily “eat” your brain’s myelin. But don’t worry—it grows back.
New research published this week in Nature Metabolism reveals a surprising effect of endurance exercise on the brain: myelin, the fatty sheath that insulates nerve fibers and supports brain function, temporarily decreases after running a marathon.
Using T2-Weighted MRI to measure myelin water fraction (a validated proxy for myelin content) researchers found up to 28% (!) reductions in key white matter tracts, particularly those involved in motor control and emotional processing. The changes were reversible, returning to baseline after two months of rest.
Why does this happen? The authors suggest a provocative idea: myelin lipids may serve as an emergency energy reserve, similar to how muscles use fat when glycogen runs low. In essence, your brain may be cannibalizing part of its own insulation to keep functioning under extreme metabolic stress.
They call this “metabolic myelin plasticity.”
While this study had a small sample (n = 10), it raises fascinating questions about brain energy use, neuroplasticity, and trade-offs involved in endurance exercise. Strenuous exercise is a known risk factor for individuals genetically predisposed to ALS – could long distance running perturb myelin homeostasis in these individuals, kicking off degenerative disease cascades? Could it be problematic in other neurological disease states?
Much more to learn—but this might reshape how we think about exercise, recovery, and brain health.
Source: Ramos-Cabrer et al., Nature Metabolism (2025)
“Reversible reduction in brain myelin content upon marathon running”
Reversible reduction in brain myelin content upon marathon running | Nature Metabolism
Text above is repurposed from one of my LinkedIn posts.
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