Does Exercise Boost Gut Health?

Here’s what the research says...

1. Exercise changes the gut microbiota

A number of studies show that engaging in regular exercise can alter the composition of gut microbes in ways generally thought to be beneficial.

For example, a 6-week aerobic endurance training programme in overweight women increased the abundance of Akkermansia, a bacterial genus that has been linked with better metabolic health. (Nature)

In other studies, moderate endurance exercise increases diversity of the microbiota (i.e. a greater range of species), which is usually considered a good sign. (Frontiers)

2. Exercise can improve gut function and reduce inflammation

Exercise doesn’t only change which microbes are there. It also seems to affect what they do, and the environment of the gut.

Moderate exercise has been shown to reduce gut permeability (i.e. reduce “leaky gut”) and reduce systemic inflammation. (Frontiers)

Improvements in metabolic markers (lipid metabolism, insulin sensitivity) are often observed alongside shifts in the gut microbiome, even when body weight doesn’t change much. (Nature)

3. But context matters

It’s not all straightforward. Here are some caveats:

Very intense or prolonged exercise (especially without proper recovery) can stress the gut: increasing gut permeability, possibly causing mild endotoxaemia (i.e. small leaks of gut bacteria products into the bloodstream), and more inflammation. (PMC)

Diet plays a big role. Many studies find that the beneficial effects of exercise on gut microbes are stronger or only clearly visible when combined with a decent diet (good fibre, plant foods, etc.). (UCLA Health)

The magnitude of effect in humans can be modest, and there is variability across individuals. Some human studies find small or no significant changes in microbial diversity, depending on the design. (Frontiers)

What Kinds of Exercise Appear Best

From what we know so far:

Moderate aerobic

e.g. walking, jogging, and light cycling are good for boosting microbial diversity, increasing SCFA producers, improving gut motility, reducing inflammation. Most human studies find benefits here.

Endurance training

e.g. longer and more intense sessions can bring benefits, especially in fitter people. It also tends to increase diversity and beneficial taxa. (Frontiers)

However, there is a risk of gut-stress during or after long, intense sessions (e.g. in ultra-endurance). Adequate hydration, nutrition, and rest are crucial when exercising for extended sessions.

Resistance training

e.g. weight lifting. There is some evidence that it helps via different pathways, possibly increases in certain beneficial bacterial groups, and metabolic function.

However, this exercise group is considerably less studied than aerobic. (MDPI)

High intensity interval training (HIIT)

e.g. circuit workouts. In theory, this exercise type could produce fast changes, as it is time-efficient and combines the benefits of all of the above variants.

However, more studies are needed, and effects may depend on how well the person tolerates high intensity activity.

What We Don’t Yet Know

Much of the evidence is from small studies or animal studies, with human trials being more limited. (Frontiers)

It’s hard to separate the effects of exercise from those of diet, lifestyle, and genetics. So far, from our understanding, diet tends to be the major confounding factor. (UCLA Health)

We’re still learning optimal “doses” of exercise for gut health (how much, how intense, how often).

Effects vary between people: age, BMI, baseline fitness, gut microbiome composition, and probably many other factors matter.

Practical Takeaways

Based on current science, here are some sensible “gut-friendly” exercise tips:

1. Be consistent

Regular moderate activity seems better than sporadic intense bursts.

2. Mix it up

Include some aerobic work, perhaps some strength training. Variety may promote more diverse gut microbes.

3. Support with diet

Diet helps feed the “good” microbes.

Eat plenty of fibre (vegetables, whole grains, legumes) and plant foods. Avoid excessive processed foods.

4. Don’t overdo it

Give your body rest and recovery; avoid pushing too hard too often without proper support, nutrition, or rest.

5. Stay hydrated

Dehydration can stress the gut.

6. Consider your fitness level

What is moderate for one person might be intense for another. Start where you are.