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The Brain: A Source of Fuel?

Author: Nikki Jiang

Editors: Hwi-On Lee and Sumire Sumi

Artist: Lalita Ma

Have you ever wondered how anyone could run a marathon? A marathon is equivalent to 105 laps around a typical track or the length of 385 football fields. How about an ultramarathon totaling 100 miles? What mechanisms allow our body to run the distance from New York City to Philadelphia? The answer lies within the organ responsible for all bodily functions: the magnificent brain. Recent studies have not only revealed that the brain controls our body, but also found evidence suggesting that tissue in the brain directly fuels endurance activities such as running a marathon. Scientists have found that endurance athletes rely on fatty tissue in the brain as an energy source, causing a major shift in our current understanding of brain functions and also expanding our knowledge of neurological diseases. 

The brain is an extremely powerful and complex organ responsible for keeping your heart beating, your lungs working, your stomach digesting, and every other function carried out by your body to maintain life. Given its many functions, the brain requires a lot of energy; 20 percent of the body’s total energy supply is used up by the brain alone. What’s using up this energy? Cells. With an outstanding 86 billion nerve cells known as neurons, the brain serves as the hub for a vast network controlling communication and transmitting signals throughout the entire body. These signals, in the form of chemicals called neurotransmitters, jump from neuron to neuron to other cells, causing a signal to be delivered. Neurons are covered by a layer of proteins and fats making up the myelin sheath, a protective coating that increases the speed and efficiency of signal transmission between neurons much like the rubber on electrical wires. Previously, researchers believed that astrocytes, support cells that fuel neurons, were the brain’s main consumer of energy. However, that may no longer be the case. Recent studies have revealed that the myelin sheath plays a critical role in fueling long-distance runners during their journeys. 

Researchers at the Center for Cooperative Research in Biomaterials (CIC) in Spain used magnetic resonance imaging (MRI) techniques to take images of the brain before and after running a marathon to find structural differences as a result of endurance activity. Brain images taken one to two days after a marathon showed a significant decrease in myelin tissue. After two weeks, myelin returned almost completely to pre-race conditions, demonstrating the rapid growth properties in the brain. These findings may be due to the massive amounts of energy burned by endurance athletes during exercise. They burn so much energy that their bodies tap into a new form of fuel supply to keep their brains active. 

These new findings are not only useful in expanding our knowledge of how the brain works, but they also offer valuable insights into the development of potential treatments for neurological diseases. Further exploring the regenerative aspect of myelin in endurance athletes can allow researchers to develop treatments for patients who have lost myelin due to neurological disease or aging. A loss of myelin in these patients is detrimental to their brain function. For marathon runners, however, it is still unknown whether or not their loss of myelin has the same negative effect. However, scientists at the CIC emphasize that these results do not suggest running is bad for the brain. It could be possible that using and regenerating the brain’s energy sources exercises metabolic functions in the brain, benefitting the runner instead. Delving deeper into the regenerative potential of myelin among endurance athletes holds promise for treating neurological diseases and also challenges assumptions of the brain’s metabolic mechanisms. 

               Now we can answer the question: how can ultramarathon athletes run 100 miles? Because of the mighty brain! 



Michaud,M.  (2020, August 5). Study sheds new light on Brain’s source of power. URMC


Ramos-Cabrer, P., Cabrera-Zubizarreta, A., Padró, D., Matute-González, M., Rodríguez- Antigüedad, A., & Matute, C. (2023, January 1). Widespread drastic reduction of brain myelin content upon prolonged endurance exercise. bioRxiv.

Rosen, M. (2023, October 31). Brain tissue may be fuel for marathon runners. Science News. 

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