This episode was made possible by the support of Yakult and produced independently by Scientific American’s board of editors.
Rachel Feltman: For Scientific American’s Science Quickly, I’m Rachel Feltman.
Over the last couple of decades, few science topics have made a bigger mainstream splash than the microbiome. Our growing understanding of the microbes that live on us, in us and around us has scientists analyzing—and trying to tweak—colonies from our armpits to our genitals. But when most of us hear the word “microbiome” our minds go first to the diverse ecosystems found within our guts.
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The communities of bacteria, archaea, viruses and fungi that live in our digestive tracts have a huge impact on us. Research shows that our gut microbiomes influence how well we digest our food and absorb nutrients, and an imbalance in the microorganisms of the gut is associated with conditions such as type 2 diabetes and nonalcoholic liver disease. Some research even suggests that our gut microbiomes are tied to cognitive function and mental well-being: scientists are exploring how autism spectrum disorder, depression, anxiety, PTSD and more could be connected to the tiny creatures that live inside us.
But this relationship isn’t one-sided: we also have a lot of power over our gut microbiomes—and that extends beyond our food choices.
Our guest today is Lydia Denworth, a contributing editor for Scientific American. She writes SciAm’s Science of Health column. In the magazine’s June 2025 issue she reported on the surprising link between gut microbes and exercise. She’s here today to tell us more.
Thanks so much for coming on to chat with us today.
Lydia Denworth: It’s good to be here.
Feltman: So you recently wrote in your column about the microbiome, which, of course, our listeners have heard a lot about, but I think people tend to think about their microbiome and think about yogurts and probiotics. But you wrote about the connection to exercise. How did you first come across that connection?
Denworth: I was at a science journalist conference, and I heard Marc Cook talk—he’s one of the people I interviewed for that column—and he’s a researcher at North Carolina [Agricultural and Technical] State University, and he studies exercise in the microbiome, and it was exactly what you just said that got him interested.
I mean, everybody thinks about diet, probiotics, things like that. And back about 15 years ago he was at the University of Illinois [Urbana-Champaign] getting his Ph.D., and the idea that there might be a link between exercise and microbes in your gut was really just not a thing that anybody was thinking about. But he did know that people with inflammatory bowel disease, specifically ulcerative colitis, benefited from exercise. So he thought, “Well, let me investigate, maybe, what that’s about.”
So he stuck mice on wheels—you know, mice like to run on wheels—and he found that the mice that voluntarily exercised were protected against a mouse version of colitis and the ones that did not run were not. And so it kinda started there, with this idea that, “Oh, there’s more to look at.”
Feltman: So now, you know, more than a decade later, what do we know about the connection between exercise and the gut microbiome?
Denworth: We know a couple of things. So one thing is: in people who are regular exercisers or who are elite athletes the diversity and abundance of microbes in your gut is greater, but more important than that is this question of, “What do the microbes actually do?” And that’s where the researchers have really kind of gone down the rabbit hole and said, “Well, why would it be that exercise is improving your fitness?”
And what they found is that exercise boosts the production of microbes that produce something called short-chain fatty acids. And that’s a simple molecule, but it’s something that helps with your gut health. It helps reduce inflammation. It is part of your healthy metabolism. So the metabolism makes energy, right, and when you exercise and then you boost these short-chain fatty acids, especially one called butyrate, it improves all these processes that your body needs to do to stay healthy.
Feltman: Can you tell us a little bit more about what the functional differences in the microbiomes of people who are getting this boost from exercise versus not? You know, what does that diversity of microbes do for us?
Denworth: There’s a lot we don’t know yet about exactly what it is that the microbes are doing versus the other benefits of exercise, so there are open questions there. But having this healthy, active microbiome that they see in athletes and from exercise seems to increase your capacity for exercise. It probably works in both directions—it’s bidirectional.
So the research on the other side of it is really only in mice so far. But they do find that if, for instance, you give mice antibiotics that kill off the bacteria in their guts, they are less likely to exercise and they reach exhaustion faster. They also find that a healthy microbiome seems to contribute to muscle development—and then vice versa, right: you don’t develop as many muscles as effectively if you don’t have a healthy microbiome.
And so all of that is in the beginning stages of research, but it—it’s intriguing, right?
Feltman: Yeah, and do the researchers behind this have any specific recommendations for what kind of exercise or how much is gonna, you know, help your microbiome out?
Denworth: So far the research doesn’t really change what the standard recommendations are, which is that we engage in about 150 minutes of moderate exercise a week or 75 minutes of intense exercise a week. The research does suggest that it’s aerobic exercise more than strength training that is having this effect—although it’s such early days and there have been so few studies of other kinds of exercise other than aerobic that I think we don’t know for sure that it’s not happening with other forms of exercise, but aerobic exercise is where it’s at. The recommendations are the same; it’s just more reason to get out there and gut out your workout [laughs].
Feltman: [Laughs] Absolutely. And remind us what’s the general advice for supporting a good, diverse, healthy gut microbiome?
Denworth: Well, diet is the number one thing that affects your microbiome—more powerfully than exercise, I should say that—and fiber in particular is really important for having a good, healthy gut. But then exercise—probably combining a healthy diet that includes a lot of fiber and doing some good aerobic exercise is going to be the best combination that’s gonna give you the healthiest gut.
Feltman: Great, so just more motivation to do the things that we already know are good for us [laughs].
Denworth: [Laughs] That’s exactly it.
Feltman: Well, thank you so much for joining us today. This has been great.
Denworth: Thanks for having me.
Feltman: That’s all for today’s episode. For more on this topic, check out Lydia’s column online or in print. If you’re not already reading Scientific American’s print magazine, you can probably find it on a newsstand near you—or go to ScientificAmerican.com/GetSciAm to subscribe. If you like this show, you’ll absolutely love the rest of the Scientific American family. As for Science Quickly, we’ll be back on Friday to talk about an insidious new trend in men’s health.
Science Quickly is produced by me, Rachel Feltman, along with Fonda Mwangi, Kelso Harper, Naeem Amarsy and Jeff DelViscio. This episode was edited by Alex Sugiura. Shayna Posses and Aaron Shattuck fact-check our show. Our theme music was composed by Dominic Smith. Subscribe to Scientific American for more up-to-date and in-depth science news.
For Scientific American, this is Rachel Feltman. See you next time!
