Two studies – one in mice and the other among humans – give us the first clear evidence that exercise alone can change the composition of microbes in your gut.

Researchers from the University of Illinois at Urbana-Champaign (USA) designed two studies to isolate exercise-induced changes in the gut from other factors (such as diet or antibiotic use) that might change the intestinal microbe environment. For the first study, the investigators transplanted fecal material from exercising and sedentary mice into germ-free mice. The germ-free mice had been raised in a sterile facility and had no microbiota of their own. For the second study, researchers tracked the changes in the composition of gut microbiota in human participants as they transitioned from a sedentary lifestyle to a more active one – and back again.

These are the first studies showing that exercise can have an effect on your gut independent or diet or other factors. In the mouse study, changes in the microbiota of recipient mice mirrored those of donor mice, with clear differences between those receiving microbes from exercising and sedentary mice. In addition, the Mayo Clinic researchers found that the recipients of the exercised mouse microbiota had a higher proportion of microbes producing butyrate (a fatty acid that promotes healthier intestinal cells, reduces inflammation, and generates energy for the host. They also proved more resistant to an inflammatory bowel disease known as ulcerative colitis.

The human study researchers recruited 18 lean and 14 obese sedentary adults. Researchers sampled their gut microbiome, and started the subjects on an exercise program during which they performed supervised cardiovascular exercise for 30 to 60 minutes three times per week for six weeks. The researchers then sampled participants’ gut microbiomes again at the end of the exercise program and after another six months of sedentary behavior. Participants maintained their usual diets throughout the study. Fecal contents of short chin fatty acids (especially butyrate) went up in the human gut as a result of exercise. These level declined after the participants reverted to a sedentary lifestyle. The most dramatic increases were seen among lean patients, with obese participants having a modest increase in short chain fatty acid-producing microbes. I’m Dr. Michael Hunter. If you enjoyed this blog, please click the Wellness! Button at the top left of this page. And consider following this blog (see comments section). Thank you!