Exercise changes gut microbiota

What we eat affects the microbes that live in our intestine, collectively known as the gut microbiota. According to two new studies, however, exercise has the same effect. Two new studies suggest that exercise independent of diet can alter the composition of gut microbiota. In mouse and human experiments, researchers discovered that physical activity independent of diet alters the composition of gut microbiota in a way that increases the production of short-chain fatty acids (SCFAs) that are beneficial for health.

The diversity of gut bacteria can be modified through exercise alone. The study included three groups of mice: one group of mice was sedentary, the other group had access to a running wheel (the exercise group), while the remaining group was sedentary and germ-free, meaning that they did not possess any gut microbiota due to being bred in a sterile environment.

The researchers took fecal material from both the exercise and sedentary groups and transplanted it into the colons of the germ-free mice. Exercise increased beneficial gut microbes
As a result of fecal transplantation, the previously germ-free mice developed gut microbiota that had comparable composition to their donor groups.

The germ-free mice that received fecal material from the exercise group had higher levels of gut microbes that produce an SCFA called butyrate, which is known to reduce inflammation and promote gut health. Additionally, when these mice were given a chemical that triggers colitis, or inflammation of the colon, the researchers witnessed a surprising response. There was a reduction in inflammation and an increase in the regenerative molecules that promote a faster recovery.

Exercise-induced modifications in the gut microbiota can mediate host-microbial interactions with potentially beneficial outcomes for the host.
Researchers included 32 sedentary adults, of whom 18 were lean and 14 were obese. The participants took part in a supervised exercise program, which involved 30–60 minutes of endurance exercise, 3 days per week, for a total of 6 weeks. Once the 6-week exercise program ceased, subjects were asked to revert to sedentary behavior for 6 weeks.

Fecal samples were obtained from each participant before and after the exercise training program, and before and after the 6-week sedentary period.
Throughout the study period, subjects continued with their usual diets.
The researchers found that all participants experienced an increase in SCFA levels especially butyrate, following the 6-week exercise program, but these levels declined when subjects reverted to sedentary behavior.

With the help of genetic testing, the researchers found that the increase in SCFA levels correlated with alterations in the levels of gut microbes that produce SCFAs, including butyrate.
The greatest increases in SCFA-producing gut microbes after exercise, the team reports, noting that their levels were much lower at baseline. Subjects who were obese experienced "modest" increases in gut microbes that produce SCFAs.
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