Gut microbes can boost the motivation to exercise

A new study by Penn Medicine uncovers a gut-to-brain pathway that increases exercise performance.

Some species of gut-dwelling bacteria activate nerves in the gut to promote the desire to exercise, according to a study in mice that was led by researchers at the Perelman School of Medicine. The study is published in Nature, and reveals the gut-to-brain pathway that explains why some bacteria boost exercise performance.

Microscopic rendering of bacteria in the large intestines.

In the study, the researchers found that differences in running performance in an animal model were largely attributable to the presence of certain gut bacterial species in the higher-performing animals. The researchers traced this effect to small molecules called metabolites that the bacteria produce—metabolites that stimulate sensory nerves in the gut to enhance activity in a motivation-controlling brain region during exercise.

“If we can confirm the presence of a similar pathway in humans, it could offer an effective way to boost people’s levels of exercise to improve public health generally,” says study senior author Christoph Thaiss, an assistant professor of microbiology at Penn Medicine.

In a yearslong process of scientific detective work involving more than a dozen separate laboratories at Penn and elsewhere, the researchers found that two bacterial species closely tied to better performance, Eubacterium rectale and Coprococcus eutactus, produce metabolites known as fatty acid amides (FAAs). The latter stimulate receptors sensory nerves in the gut, which connect to the brain via the spine. The stimulation of these CB1 receptor-studded nerves causes an increase in levels of the neurotransmitter dopamine during exercise, in a brain region called the ventral striatum.

The striatum is a critical node in the brain’s reward and motivation network. The researchers concluded that the extra dopamine in this region during exercise boosts performance by reinforcing the desire to exercise.

Read more at Penn Medicine News.