Running a marathon causes the brain to start eating itself, research shows

Gross

Our bodies get battered enough when running a marathon, now new research suggests our brains could also be impacted.

Many of us don’t need much to deter us from running a marathon – the pain, head noise and hours dedicated to training are enough. But marathons are having a moment. It feels like everyone we know is posting stories of their daily trots before sharing their finish line photos months later.

Without looking into it, you can probably predict that running for four hours on hard roads will wreak havoc on your body, but I’ll bet you hadn’t considered this health effect. 

New research published in Nature Metabolism shows running a marathon can cause the brain to start eating itself.

Energy sources fuelling your run

Running has a lot of notable benefits, including boosting cardiovascular health, building muscle, strengthening joints and improving your mental health, but marathon running can put the body under severe stress.

During any workout, our bodies burn through carbohydrates for energy before turning to fat stores and proteins. 

Running has a lot of notable benefits, including boosting cardiovascular health, building muscle, strengthening joints and improving your mental health, but marathon running can put the body under severe stress.

Our brains consume around 20 per cent of the body’s energy, so if there aren’t enough energy sources readily available, it will certainly look for others.

Neuroscientist and 18-time marathon runner Carlos Matute, along with his research team, wanted to assess the brain’s reserve energy sources, and found that the fatty tissue that coats nerve cells could be an option.

Neuroscientist Pedro Ramos Cabrer co-authored the study. He said, "we needed to really deplete all the sources of energy of a body to prove this".

Our brains consume around 20 per cent of the body’s energy, so if there aren’t enough energy sources readily available, it will certainly look for others. Image: Pexels

How can the brain eat itself?

The team conducted MRI scans of the brains of 10 marathon runners 48 hours prior to their event, and again two days, two weeks and two months after. 

The fatty substance myelin makes up close to 40 per cent of the brain. The researchers found levels were depleted post-run, and MRI signals in 12 areas of the brain were depleted by up to 28 per cent two days post-marathon. 

"The areas that we saw have more significant changes were those related to motor circuits and the center of emotional control of the brain," Cabrer said.

The researchers found levels were depleted post-run.

Can the damage be permanent?

This isn’t to say you need to withdraw from your upcoming marathon just yet. The team found that all of the runners’ myelin measures had returned to baseline levels two months after their big runs.

But this is your sign to make sure you’re carbed up pre-run so your body’s got more than enough fuel to get through.

Originally published as Running a marathon causes the brain to start eating itself, research shows