Effects of Exercise on Gut Microbiota of Adults: A Systematic Review and Meta-Analysis.

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• The gut microbiota and host relationship is dynamic, playing a critical role in maintaining physiological and metabolic functions.
• External and internal factors, such as exercise, age, and gender, can significantly influence gut microbiome composition and function.
• Studies on exercise’s effect on the gut microbiome have yielded mixed results, likely due to variations in exercise types, participant demographics, and study designs.
• This meta-analysis provides insights into the overall impact of exercise on gut microbiome diversity in adults, highlighting changes in specific bacterial species.

Introduction

A systematic review and meta-analysis was conducted to investigate the effect of exercise on the diversity of the gut microbiota in adults.

Method

• This study was registered with PROSPERO and followed the Preferred Reporting Items for Systematic Reviews and Meta-analyses (PRISMA) guidelines.
• Included studies measured changes in gut microbiota in adult participants (aged 18-75) that included athletes, non-athletes, obese, and sedentary people.

Results

A total of 25 studies, involving 1044 participants aged 16 to 70 years were included. Most studies included both genders, while nine focused solely on males and four on females. The exercise interventions consisted of high-intensity interval training (HIIT), moderate-intensity continuous training (MICT), aerobic exercises, and resistance training. Gut microbiota composition was assessed at both the phylum and genus levels. Most studies were randomised-controlled trials, with some utilising crossover designs. The results showed a low risk of bias and the quality of included studies was deemed reliable.

• Analysis of 19 studies using the Shannon Index revealed notable changes in gut microbiome diversity following exercise (CI from 0.001 to 0.092, z-value of 1.993, p = 0.046).
• Conversely, the Simpson Index (CI from 0.009 to 0.014, z value 0.431, p=0.666), the Chao1 Index (z-value, p=0.423), and the phylogenetic Index (p= 0.063) did not show an effect of exercise on gut microbiome diversity.
• The meta-analysis reviewed the effect of exercise on specific bacterial species and reported a significant decrease in the abundance of Bacteroidetes (p=0.013) and a highly significant increase in Firmicutes (p=0.0001).
• Proteobacteria, often associated with inflammatory conditions, did not show post-exercise changes. (p= 0.212).
• Subgroup analysis revealed that females and older adults exhibited more pronounced changes in gut microbiome diversity following exercise than males and younger participants.

Conclusion

This systematic review and meta-analysis found that exercise led to increased gut microbiome diversity in adults. The exercise interventions were associated with a higher abundance of Firmicutes and a lower abundance of Bacteroidetes.

• The balance between gut microbiota and the host is crucial for overall health maintenance.
• Emerging evidence indicates that exercise may modulate the composition and functionality of gut bacteria.
• This systematic review and meta-analysis suggest that exercise may influence gut microbiome diversity in adults.

• These findings emphasise the need for a deeper understanding of how different types of exercise selectively affect various aspects of the gut microbiome.
• Future research should consider standardised methodologies to elucidate better the mechanisms by which exercise impacts gut microbiome diversity.