What Exercise Is Doing to Your Gut Health

Exercise has clear benefits for many measurable indicators of health. It’s been linked to a lower resting heart rate, a higher VO2 max, lower blood pressure, and lower total body fat. Being active protects people against heart disease, type 2 diabetes, and even some cancers. Spending less time sedentary (sitting or lying down while you’re awake) lowers those risks too. Exercise is prescribed as a treatment for a variety of chronic diseases, anything from depression to osteoarthritis.

But we almost never hear about what exercise is doing for your gut. Is there a connection? And if so, how exactly does exercise improve your gut health?

Does Exercise Change Your Gut Microbiome?

Your microbiome is an ecosystem of trillions of microscopic cells that live inside your gut. Within the microbiome are hundreds of species of bacteria, which researchers can measure. Richness refers to the number of different species that live in your gut, and microbiome diversity also accounts for the ratios they exist in. Typically, greater diversity is linked to a healthier microbiome that can do a variety of jobs that help keep your gut working.

So looking at diversity can show whether exercise actually builds a better gut microbiome.

We can start with athletes, since they’re far more active than the average person.

A data analysis comparing the microbiomes of over 300 athletes to non-athletes didn’t find many differences.

Athletes tend to have slightly richer microbiomes than non-athletes, but diversity is about the same. Studies like these don’t account for any differences in diet, which can have effects on the microbiome as well.

When researchers ran a 24-week exercise trial, they weren’t able to detect a change in diversity either.

They split young, inactive adults into groups that did either no exercise, moderate exercise, or vigorous exercise. Microbiome diversity remained the same between exercisers and non-exercisers.

That’s just one trial though. When researchers pooled data from studies in adults 55 and older, they found a small rise in diversity with exercise, with a larger rise in people who weighed more.

So how do we make sense of all these differing results? Well, one way to interpret this data is that your microbiome may only change up to a certain point. Athletes and non-active yet healthy populations both are considered healthy in the sense they are without an active diagnosis, and their microbiomes are about the same. In unhealthy populations with diagnoses like obesity, the microbiome is altered. Activity in these populations improves their health and possibly the microbiome alongside it. That’s just my theory. But the microbiome isn’t the whole story of the gut. What else can exercise do for your gut?

Does Exercise Help Digestion?

The main function of your gut is to move food through it and digest it. This function can become altered, resulting in constipation and slower transit. Some people also get uncomfortable gut symptoms like stomach pain and bloating. Can exercise do anything to improve these issues?

Constipation and regularity

Constipation usually comes from a problem with the colon, rectum, pelvic floor, or anus. It can look like straining, fewer than 3 bowel movements a week, lumpy or hard stools, or feeling blocked up or like you haven’t fully emptied.

When researchers assessed 13 studies of nearly 120,000 people total, the most active among them had about a 31% lower risk of constipation than the least active. Even meeting general activity guidelines was linked to about a 13% lower risk of constipation.

So how exactly does exercise help?

Well, there are a few ideas behind this. Your gut, including your colon, is lined with muscle. It’s a different type of muscle than we normally picture, but it can still contract and relax like any other muscle. These contractions are what move your stool along the digestive tract. Researchers propose that physical activity can stimulate these contractions, which helps your gut move things along at a normal speed. Other authors in the field propose that contracting your abdominal wall during physical activity causes a reflex that boosts the gut’s pushing movements.

Transit time

Transit time is the time it takes for food to travel through your entire digestive tract and exit out the other end. A longer transit time is linked to constipation.

A research trial showed that transit time in the colon sped up over 25% in inactive adults with chronic constipation. This was over a 12-week period of 30-minute brisk walks combined with a daily eleven-minute home exercise program.

In a small study of 10 healthy volunteers, each person spent 1 week each either running on a treadmill, riding a stationary bike, or resting, for 1 hour a day. After the week was up, they would rotate activities for the next week.

Researchers found that during exercise weeks, their gut transit time sped up by about a third.

These studies are small, so larger studies could help show whether exercise consistently and meaningfully speeds up gut transit time in broader populations.

IBS

Symptoms of irritable bowel syndrome (IBS) include bloating, abdominal pain, and constipation or diarrhea.

In a trial of over 100 people with IBS, people who were counseled by physical therapists to be more active improved their symptom scores more than people who weren’t counseled at all.

The exercisers reported less intense symptoms after only being encouraged to exercise. No part of the study actually gave these patients an exercise program to follow, so how they exercised was up to them. Even so, it seemed to work out to their benefit. This result suggests that even unstructured programs can help improve symptoms in people with IBS.

Trials of structured exercise programs for IBS exist, but right now, it’s unclear which type of exercise is the best, and how often and how much people with IBS should exercise. The biggest takeaway is that moving more can help.

Inactivity and the Gut

The effects of exercise on the gut seem promising. But what happens to your gut if you don’t get any activity?

When a group of over 8,000 people wore activity trackers, those who spent more of their day sitting tended to have lower microbiome diversity than those who spent more time in moderate or vigorous activity. Even among people of similar body size, more activity was still linked to higher diversity, though the differences were small.

In two small studies, 6 to 8 weeks of training changed people’s gut bacteria, and those changes faded once they stopped exercising. This suggests that exercise has to be consistent in order for any helpful changes to last.

But what about outside of the microbiome?

In a survey of nearly 17,000 middle-aged and older adults, people who reported being less active in their free time also reported more gut symptoms, bloating included. Again, people who move more tend to have fewer complaints about their gut.

How Much Exercise and What Kind?

Most studies use aerobic exercise when measuring the effects of exercise on the gut. That includes walking, jogging, cycling, or anything that raises your heart rate for an extended period of time. Every study we’ve looked at used a different program. There isn’t a definite “gut protocol” for exercise. A recent review says that an exact exercise dose needed to change the microbiome is currently unknown.

What’s helpful to know is that meeting the general activity guidelines was linked to about a 13% lower risk of constipation. Following them would likely benefit your gut in addition to providing other health benefits. The general recommendations are at least 150 minutes per week of moderate exercise, which includes brisk walking or slow cycling, or at least 75 minutes per week of vigorous exercise which includes running, swimming, or fast cycling.

In Summary

While there isn’t a set protocol that guarantees a healthier gut, there do seem to be general principles we can apply. Moving more, in general, is associated with a healthier gut that experiences fewer symptoms. Move in any way you can. Going for a short walk after meals, or walking around your office or home to break up long periods of sitting are some ways to quickly get some daily activity.

Consistency is also important. In the small studies we have, changes in the gut faded after stopping exercise. Staying consistent helps your body keep the benefits long term.