Exercise for your Gut Bacteria

It is fascinating that more than 30 trillion microorganisms live in our colon, which means that about 50% of the total number of cells in the human body are human cells and the other 50% are bacterial cells. We rely on these bacterial cells for our health and survival, however our body is constantly trying to find a balance between the Good and the Bad bacteria.


The Good colon bacteria help keep us healthy and suppress inflammation, while the Bad colon bacteria increase our risk for heart attacks, strokes, diabetes, colitis, certain cancers, chronic inflammation and autoimmune diseases.


The Good colon bacteria produce short chain fatty acids (butyrate) that increase the number and size of mitochondria in our cells for producing energy.


It is well known that diet affects the growth of Good and Bad colon bacteria, but studies on mice and humans now show that exercise helps the growth of Good bacteria and reduces the number of Bad ones. What is surprising to the researchers is that exercise was able to do this without any dietary changes.

This 2017 study looked at the impact of exercising on the metabolic output of the gut microbiota found in fecal samples.

Previously inactive subjects (obese & lean) received 6 weeks of supervised, progressive exercise training at 3 times a week.

The exercise was progressed from 30 to 60 minutes/day of moderate to vigorous intensity.


After the 6-week exercise program, all the subjects were instructed to return to their original sedentary lifestyle for a 6-week washout period.

Three different fecal samples were collected from each participant; once before and once after the 6-week exercise program. The third sample was collected after the sedentary washout period.

1st sample pre-exercise:

Reduced  Good bacteria; Increased Bad bacteria


2nd sample post-exercise:

Increased Good bacteria; Reduced Bad bacteria


3rd sample return to sedentary lifestyle:

Reduced Good bacteria; Increased Bad bacteria


A healthy gut is anti-inflammatory and an unhealthy gut is inflammatory. Perhaps this partially explains why aerobic exercises have been found to be beneficial for those with hip and knee OA and those with persistent LBP.


Simplified conclusion: A regular moderate to vigorous exercise program has the potential to positively influence the 30 trillion bacteria found in our body; however the potential benefit does not last if exercise is stopped.

In a nutshell: You now have two more reasons to promote physical activity, firstly to rejuvenate your mitochondria and secondly to improve the health of your colon and reduce inflammation.


Reference: Allen J et al Exercise Alters Gut Microbiota Composition and Function in Lean and Obese Humans. Med Sci Sports Exerc. 2017 Nov 20.

Fecal samples

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