Aerobic Fitness and Microbiome – Can Aerobic Exercise Improve Gut Health?

We all intrinsically know that exercise is good for us, but when it comes time to actually put on the running shoes and hit the trail, suddenly we think of a million and one reasons (read excuses) to put it off. A recent study suggests yet another reason to get your run on. Your gut and all of the billions of creatures living inside of you (yes, there are more creatures inside/on you than you have cells) would actually benefit from more aerobic activity.

The microbiome is a fascinatingly complex system that we do not truly understand, but researchers are continuing to study the relationship between our bodies and the billions of bacteria that live symbiotically with us throughout our lives. There is the case of the average weight woman who had a fecal transplant from an obese donor and subsequently became obese after her surgery. Science is trying to figure out the relationship between our gut bacteria and our overall health.


More and more evidence suggests that having a diverse microbial community in our intestines is a prerequisite of being healthy and having a strong immune system. So, how does one develop a healthy microbiome? I won’t pretend to have all the answers, but the below is what has been deduced thus far.

  • Eat a diet high in fruits and vegetables (fiber), lean meats (protein), Omegas (healthy fats), and fermented foods. You know, the stuff your mom would call “good for you food”
  • Don’t be afraid to get your hands dirty
  • Avoid taking antibiotics for your cold that will just go away in a couple of days anyway
  • Exercise

Wait, what? I can see the first three, but what does exercise, especially aerobic exercise have to do with gut bacteria? Research has now come out that suggests that people who demonstrate higher levels of cardio-respiratory fitness (CRF) also have a more diversified microbiome. So, not only is CRF considered a better predictor of mortality than smoking, diabetes, and hypertension, it also has outperformed other variables (sex, age, BMI, and dietary components) when it comes to gut health and diversification.

Ok, if you say so, but why would this be? As it turns out, there is a correlation between our aerobic fitness (measured as VO2peak) and the metagenomic functions of the micro biome. In layman’s terms, this is how that bacteria interacts with us and each other. Intrinsic adaptations to endurance training can lead to changes in the GI tract like a decrease in blood flow to the area, tissue hypoxia, increased transit, and increased absorptive capacity. It may also change the gut pH, which in turn may create an environment more suitable for a richer community diversity.

Endurance 1

Another interesting find is that VO2peak is inversely correlated with lipopolysaccharide (LPS) biosynthesis and its associated proteins. LPS is a major component of gram negative bacteria cell walls and is considered an endotoxin when in the blood and subsequently elicits a strong inflammatory response. This response is highly associated with obesity and other metabolic syndromes. Exercise training attenuates inflammation in part by reducing blood LPS, which suggests that gut microbiota adapt to metabolic demands of an active lifestyle.

So, the next time you start to make excuses as to why you can’t go out for a run, keep in mind that diet alone can’t make you healthy. Aerobic exercise is not going to kill your gains, and in fact, it may actually aid in the absorption of all the protein and BCAAs that you take in.