Our gut microbes love a good workout

Our gut microbes love a good workout

Exercise does more than make us hot and thirsty. It can have big effects on the trillions of microbes that live in our gut. Each one-celled organism is tiny. Together, their huge community, known as the gut microbiome (My-kroh-BY-oam), can weigh up to 2 kilograms (4.4 pounds). Its microbes can offer mighty benefits. They help digest food to extract the energy our bodies need. They help fight infections. They may even affect our mood. Technology can now gauge the activity of these microbes — and how it changes with exercise.

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Lucy Mailing is a nutritional scientist. She earned her PhD at the University of Illinois Urbana-Champaign. There, she was part of a team that studied how exercise affects the gut microbiome.

The researchers recruited 32 men and women who were fairly inactive. For six weeks, each recruit exercised three days a week. They worked out on a treadmill or bike, starting at 30 minutes per day. Over the weeks, they gradually increased the workouts to 60 minutes.

Scientists Say: Microbiome

The researchers wanted to see how becoming active might affect someone’s gut microbes. And to find out, they didn’t have to open anyone up. They just had to wait for a share of the microbes to come out — in poop. Each recruit collected some of their feces before the study began. They did it again right after the six weeks of exercise ended. Six weeks after that, they collected one last sample of poop.

During the workout weeks, the recruits did not change what they ate — except for three days before each poop collection. For those days only, each of the recruits followed a menu designed just for them. It included only foods and drinks from their usual diet.

Scientists Say: Fatty acid

Collecting poop is yucky. Receiving and processing it is, too. But working through this yuckiness yielded new insights. For instance, the recruits’ microbes made more short-chain fatty acids (SCFAs) that are good for health. One of these was butyrate [BYOO-tur-ayt]. Studies have shown it can protect against certain cancers, fight inflammation and regulate genes that promote health. It may even enhance sleep. Our gut bacteria make such SCFAs from the fiber found in nuts, grains and many vegetables.

Artist’s portrayal of the trillions of microbes in our digestive tract living among the finger-like projections of the gut wall. Scientists find that regular exercise boosts the beneficial chemicals these microbes make and the makeup of their community.CHRISCHRISW/ISTOCK/GETTY IMAGES PLUS

By the end of the study, the recruits had more SCFA-producing microbes than at the start. This was especially true in lean people. And those with more of these bacteria lost more body fat during the six weeks of exercise. Their fitness also improved more quickly.

But once people stopped exercising, their gut microbiomes went back to what they had been before the study. This shows that “regular exercise changed the composition and activity of the gut microbes,” Mailing says. And the benefits of exercise in these people had likely been helped along by those microbes, she adds.

Her team shared its findings in the April 2018 Medicine & Science in Sports & Exercise.