Scientists at Edith Cowan University have discovered that the gut microbiome changes with training intensity. These shifts may hold hidden clues about performance, recovery, and overall health. Credit: Shutterstock
Exercise intensity affects the gut microbiome, shifting bacteria and gut health markers. Diet and rest patterns also contribute to these changes.
Exercise is widely known to benefit both mental and physical health, but new findings from Edith Cowan University (ECU) suggest that the intensity of training may also influence the gut microbiome.
PhD candidate Bronwen Charlesson conducted a study examining how different training loads, both high and low, affect athletes’ gut health. Her goal was to better understand these changes so athletes could optimize their health, wellbeing, and performance by considering the role of the microbiome.
“Based on previous research, it appears that athletes have a different gut microbiota when compared with the general population. This includes greater total short chain fatty acid concentrations, alpha diversity, an increased abundance of some bacteria and a lower abundance of others,” she explained.
Charlesson added that the distinction between athletes’ microbiomes and those of non-athletes could be influenced by dietary habits, but fitness indicators such as oxygen uptake have also been linked to these differences.
Training load and bacterial shifts
Her research demonstrated that training intensity directly affected gut health markers in athletes. Variations were observed in short-chain fatty acid levels and in the populations of specific bacteria.
Although not formally measured in this study, Charlesson pointed to elevated blood lactate from high-intensity exercise as a possible contributor. Lactate produced in the muscles is transported to the gut for metabolism, which may promote the growth of certain bacterial species.
Ms Charlesson noted that the changes found in the gut biome when comparing high training loads to low training loads, were also related to diet.
Diet changes during rest periods
“During low training load times, or periods of rest, athletes are often more relaxed about their diets, in this study we saw no change in total carbohydrate or fiber intake during periods of rest, but we did observe a decline in the diet quality of food eaten. This decline was related to increases in processed fast foods, decreases in fresh fruit and vegetables, and a moderate increase in alcohol intake. These changes did impact the composition of the gut microbiome.
“Another observation made during the research was the significant slowing of gut transit times in athletes during low training loads. That slowing of transit time during the low training load appears to also be impacting the gut microbiome for an athlete.”
Ms Charlesson explained that while it’s still unclear exactly how the gut influences athletic performance, there are some promising clues. For example, the gut may play a role in lactate metabolism and regulating pH levels, both of which could impact performance and overall athlete health. However, more research is needed, particularly into factors like training load, diet quality, and gut transit time, to better understand how these elements can be adjusted to enhance athletic performance.
Reference: “Training load influences gut microbiome of highly trained rowing athletes” by B. Charlesson, J. Jones, C. Abbiss, P. Peeling, S. Watts and C.T. Christophersen, 21 May 2025, Journal of the International Society of Sports Nutrition.
DOI: 10.1080/15502783.2025.2507952
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