(Researchers) began by recruiting 32 men and women who did not exercise. About half were obese and the rest of normal weight.
The scientists took blood and fecal samples and tested everyone’s aerobic fitness. Then they had the men and women begin supervised workouts, during which their efforts increased over time from about 30 minutes of easy walking or cycling to about an hour of vigorous jogging or pedaling three times per week.
The volunteers were asked not to change their normal diets.
After six weeks, the scientists collected more samples and retested everyone, and then asked the volunteers to stop exercising altogether.
Six weeks later, the tests were once again repeated.
The subsequent analysis showed that the volunteers’ gut bugs had changed throughout the experiment, with some increasing in numbers and others declining. The researchers also found changes in the operations of many microbes’ genes. Some of those genes were working harder now, while others had grown silent.
Most of these changes were not shared from one person to the next. Everyone’s gut responded uniquely to exercise.
But there were some similarities, the researchers found. In particular, they noted widespread increases in certain microbes that can help to produce substances called short-chain fatty acids. These fatty acids are believed to aid in reducing inflammation in the gut and the rest of the body. They also work to fight insulin resistance, a precursor to diabetes, and otherwise bolster our metabolisms.
Most of the volunteers had larger concentrations of these short-chain fatty acids in their intestines after exercise, along with the microbes that produce them.
These increases were greatest, though, among the volunteers who had begun the experiment lean compared to those who were obese, the scientists found.
And perhaps not surprisingly, almost all of the changes in people’s guts dissipated after six weeks of not exercising. By and large, their microbiomes reverted to what they had been at the study’s start.
Still, the study’s overall results suggest that even a few weeks of exercise can alter the makeup and function of people’s microbiomes, says Jeffrey Woods, a professor of kinesiology and community health at the University of Illinois who conducted the study, along with his doctoral student Jacob Allen (now a postdoctoral researcher at Ohio State University) and others.
In theory, Dr. Woods continues, these changes could contribute to some of the broader health benefits of exercise, such as its ability to reduce inflammation throughout the body.
“But more studies need to be done to prove this,” he says.
This is really interesting because it gives a physical reason for why exercise helps reduce diabetes. Also more info on the biome.