The microbiome influences exercise interest

A recent study in Nature shows that, at least in the case of mice, the microbiome dictates interest in exercising - or not.

In this study, the microbiome profile of mice who were avid exercisers was compared to the microbiome of “lazy” mice.

Mice bred in the University of Pennsylvania’s lab have individual profiles. Some are exercisers, some are not. The exercisers had bacteria that produce fatty acids, triggering endorphins that cause the “runner’s high” I find so elusive, thereby creating a positive-reinforcement loop. When the exercisers were treated with antibiotics to kill their microbiomes, they became lazy. When their original microbiome was restored, they became active again.

They also studied germ-free mice, mice raised in very controlled conditions to remain sterile. These mice are not interested in exercise, but when given some of the bacteria from the exercisers (this is done by letting the mice eat each other’s poop - mice love to eat poop), they became exercisers.

The exercise-associated bacteria send a signal that blocks dopamine breakdown, resulting in higher levels of dopamine, the “happy hormone,” that stay around longer.

The runner’s high, explained.

As always, mouse are very different than humans, so mouse data cannot be directly extrapolated to humans. But there is human data that suggests a similar mechanism is at play.

Marathon runners were found to have higher numbers of a bacteria called Veillonella atypica, which breaks down lactate, the substance that causes muscle soreness. During running, the numbers of this bacteria increase. This may explain why some runners can run for long periods of time while seemingly unaffected, and others, like myself, cannot.

Citations:

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).

Scheiman J, Luber JM, Chavkin TA, MacDonald T, Tung A, Pham LD, Wibowo MC, Wurth RC, Punthambaker S, Tierney BT, Yang Z, Hattab MW, Avila-Pacheco J, Clish CB, Lessard S, Church GM, Kostic AD. Meta-omics analysis of elite athletes identifies a performance-enhancing microbe that functions via lactate metabolism. Nat Med. 2019 Jul;25(7):1104-1109. doi: 10.1038/s41591-019-0485-4. Epub 2019 Jun 24. PMID: 31235964; PMCID: PMC7368972.