Researchers have discovered that a fatty substance called myelin, which insulates electrical signals in nerve cells, may also serve as an energy source for the brain during intense physical activity, such as marathon running.
Using magnetic resonance imaging (MRI) scans of long-distance runners’ brains before and after completing marathons, scientists found that levels of myelin decreased significantly in areas involved in motor control, sensory perception, and emotions. However, these changes were temporary, with myelin levels returning to normal within two months.
The study’s lead author, Carlos Matute, suggests that the reduction in myelin may be a strategic use by the brain to power itself during periods of low energy. “These findings open the way to consider that myelin lipids contribute to brain energy metabolism, at least in certain conditions,” he said.
Researchers also found no significant impact on cognitive function following the marathons, with some even suggesting that the temporary loss of myelin may be beneficial as it teaches the brain how to repair its metabolic machinery. The study’s findings have implications for our understanding of brain energy metabolism and may provide new insights into optimal training strategies for endurance athletes.
Source: https://www.nature.com/articles/d41586-025-00864-z