Benefits of exercise-boosted gut dependent on weight and regimen: Study

By Will Chu

- Last updated on GMT

New study findings appear to back assertions that exercise is good for gut diversity, as US researchers also discover that obesity and exercise regularity to be significant influencers of this benefit.

Writing in Medicine & Science in Sports & Exercise, ​the team found that exercise-induced alterations of the gut microbiota were dependent on obesity status.

Researchers discovered exercise increased faecal concentrations of short-chain fatty acids (SCFAs) in lean, but not obese, participants with exercise-induced changes largely reversed once exercise ceased.

Exercise’s gut benefits may even extend to gut disorders as the study concluded, “Exercise-induced shifts in the gut microbiota and SCFAs may have implications for diseases of the gut”.

“Physical activity has been shown to reduce risk of colorectal cancer and irritable bowel disease (IBD).

“Butyrate is a primary fuel source for colonocytes, is required for maintaining gut barrier function, and is a critical metabolite regulating the anti-inflammatory/regulatory phenotypes of gut-resident immune cells.”

Exercise-induced changes in the gut microbiota are an emerging area in sports nutrition that have garnered much interest from firms looking to tap into the lucrative and growing sector.

Physical activity has previously been correlated with alterations in metabolism, immunity, and even behaviour.

Exercise training also increases microbiota-derived short chain fatty acids (SCFAs), which serve as an energy source for a variety of tissues and have been shown to reduce inflammation and improve insulin sensitivity.

Rugby players’ gut

NutraIngredients has reported on a spate of similar studies​ that establish this relationship. These include the study results that show the positive influence of endurance training on gut microbiota composition.

In addition, cross-sectional human studies have found professional rugby players differ from body mass index (BMI)-matched non-athletes in several bacterial phyla.

In this study, the research team from University of Illinois at Urbana-Champaign began looking at the impact of six weeks of endurance exercise on the gut microbiota in lean and obese adults on varied diets.

Thirty-two lean (18 [9 female]) and obese (14 [11 female]), subjects participated in six weeks of exercise for three days per week that progressed from 30 to 60 minutes per day and from moderate (60% of heart rate reserve [HRR]) to vigorous intensity (75% HRR).

Afterwards, subjects returned to a sedentary lifestyle activity for a six-week washout period. Faecal samples were collected before and after six weeks of exercise, as well as after the sedentary washout period, with 3-day dietary controls in place prior to each collection.

Results revealed that exercise-induced alterations of the gut microbiota were dependent on obesity status.

Exercise increased faecal concentrations of short chain fatty acids (SCFAs) in lean, but not obese, participants.

Additionally, exercise induced microbiota metabolism changes that mirrored changes in bacterial genes and taxa capable of SCFA production.

Lastly, exercise-induced changes in the microbiota were largely reversed once exercise training ceased.

“Further highlighting the BMI-dependent response to training, exercise-induced shifts in SCFA-producing taxa (Faecalibacterium spp. and Lachnospira spp.),”​ the study specified.

Mechanisms of action?

The research team could not confirm the mechanism(s) responsible for exercise-induced increases in faecal SCFA concentration.

They theorised that the increased production of SCFA through endogenous metabolic input (e.g. lactate), increased mixing of intestinal contents and bacterial fermentation of dietary fibres.

This in turn increased anaerobic fermentation due to colonic oxygen saturation or pH changes, or reduced intestinal utilisation and uptake of SCFA.

Further analysis of the findings pointed to changes in Faecalibacterium spp​ number, which has been shown to induce anti-inflammatory effects and may be protective against bowel diseases.

“Thus, we postulate that exercise-induced shifts in SCFAs, butyrate-producing taxa and metabolic capacity to produce SCFA may have the potential to prevent the occurrence or offset the symptomology of IBD. Future studies are needed to address these hypotheses more closely.”

Source: Medicine & Science in Sports & Exercise

Published online: doi: 10.1249/MSS.0000000000001495

“Exercise Alters Gut Microbiota Composition and Function in Lean and Obese Humans.”

Authors: Jacob Allen et al.

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