Gut Health & Exercise: The Surprising Science Behind Motivation

Could your gut health be the reason for your lack of motivation for exercise? In a study published in the journal Nature, researchers looked at why some mice used their exercise wheel a lot versus others mostly ignored it.

The researchers used a machine-learning algorithm to look at a wide range of factors, including genome sequences, gut bacteria species, and bloodstream metabolites that could possibly explain the varied activity levels among mice.

Surprisingly, the researchers found that genetics seemed to have little to do with activity level. Instead, gut bacteria seemed to be the key driver to mice’s motivation to exercise.

When researchers gave mice broad-spectrum antibiotics, wiping out their gut bacteria, the distance the mice ran decreased by 50%. The researchers then sequenced RNA in the mice striatum, the part of the brain responsible for motivation. They found reduced levels of dopamine compared to controls. Thus, antibiotic-treated mice were getting less of a dopamine hit after their run.

Over several years of very innovative experiments, researchers identified two bacteria strains tied to better performance: Eubacterium rectale and Coprococcus eutactus. These bacterial species produce fatty acid amides that interact with endocannabinoid receptors in the gut.

Endocannabinoid receptors signal the brain to decrease monoamine oxidase. Monoamine oxidase is a compound that breaks down dopamine. Thus, decreasing monoamine oxidase leads to an increase in dopamine. This results in mice getting the feel-good effect of exercise and wanting to do it again.

Now the real question is, does this gut-brain pathway also apply to humans? In other words, could changing our gut microbiome help us to keep our new year’s resolution of exercising? Fortunately, those studies are already underway.

Reference:

Dohnalová, L., Lundgren, P., Carty, J.R.E. et al. A microbiome-dependent gut–brain pathway regulates motivation for exercise. Nature 612, 739–747 (2022). https://doi.org/10.1038/s41586-022-05525-z