The intestinal microbiota, the set of microorganisms that inhabit my digestive tract, is one of the most cutting-edge subjects in medical research. We now know that it plays a central role in immunity, mood regulation (via the gut-brain axis), carbohydrate and lipid metabolism, and the prevention of many chronic diseases. What is less known is that physical activity is one of the most powerful modulators.
Research on the exercise-microbiota axis is still young, the first large-scale studies date from the 2010s, but its results are already striking. Athletes have a microbiota that is significantly more diverse and richer in beneficial bacteria than sedentary people, regardless of their diet. And these differences have direct consequences on overall health.
1. The intestinal microbiota: an organ in its own right
The intestinal microbiota includes more than 100,000 billion microorganisms belonging to more than 1,000 different species. Its total weight is approximately 2 kg, comparable to that of the liver. It performs essential functions:
2. How exercise changes the microbiota
The reference study on this subject (Clarke et al., Gut 2014) compared the microbiota of 40 Irish professional rugby players with two groups of sedentary people. Athletes had greater microbiotic diversity and higher levels of beneficial bacteria like Akkermansia muciniphila, associated with metabolic health and obesity prevention.
But the crucial question is: are these differences caused by exercise or by the athletes' different diets? Studies in mice and controlled interventions in humans have since shown that exercise alone, independent of diet, modified the composition of the microbiota. Here are the mechanisms identified:
- ●Increased intestinal transit: exercise accelerates peristalsis (intestinal movements), reducing the contact time of carcinogens with the mucosa and modifying bacterial growth conditions.
- ●Reduction of intestinal inflammation: moderate exercise reduces pro-inflammatory cytokines that disrupt the microbiotic ecosystem and promote dysbiosis (imbalance).
- ●Increased short-chain fatty acids: Active people have higher levels of butyrate, the main source of energy for cells in the intestinal mucosa and a powerful local anti-inflammatory.
- ●Modification of bile composition: exercise modifies the composition of bile acids, which directly influence the selection of intestinal bacterial species.
3. Microbiotic diversity: the key indicator
Microbiota diversity, the number of different species and their balance, is considered the best indicator of microbiotic health. A microbiota poor in diversity is associated with obesity, metabolic diseases, chronic inflammation and autoimmune diseases.
- ●Endurance athletes: they systematically present a greater microbiotic diversity than sedentary athletes, with an increased prevalence of bacteria such as Faecalibacterium prausnitzii (anti-inflammatory) and Akkermansia muciniphila (metabolic health).
- ●Exercise intensity and diversity: studies show a dose-response relationship: the more regular and moderate the physical activity, the higher the diversity. Very intense exercise (marathon, ultra-trail) can temporarily reduce diversity, again illustrating the J-curve.- The speed of changes: measurable changes in the microbiota are observed after just 6 weeks of regular exercise in previously sedentary people (Durk et al., Medicine & Science in Sports & Exercise 2019).
4. The gut-brain-muscle axis: triangular communication
The most fascinating discovery of this decade is that of the gut-brain-muscle axis, a bidirectional communication between the gut, brain and muscles, mediated by microbiotic metabolites, the autonomic nervous system and hormones.
- ●The microbiota influences performance: studies in mice (Scheiman et al., Nature Medicine 2019) show that the administration of bacteria producing propionate (a short-chain fatty acid) increases endurance performance. Similar preliminary results are observed in humans.
- ●The microbiota influences mental health: the microbiota produces neurotransmitters (GABA, serotonin, dopamine) which influence mood, stress and cognition via the vagus nerve. A diverse microbiota is associated with better resilience to stress.
- ●Exercise influences microbiotic metabolites: physical effort increases the production of beneficial microbiotic metabolites (butyrate, propionate) which in turn supply muscle and intestinal cells.
5. How to optimize your microbiota through physical activity
The most effective combination for a healthy microbiota combines regular physical activity with a diet rich in fiber and fermented foods, the two interventions potentiate each other:
- ●Regular moderate exercise: 150 minutes of moderate activity per week is enough to produce positive changes in the microbiota. Episodic very intense exercise has less effect than regular moderate exercise.
- ●Dietary fibers: fibers are the main substrate of beneficial bacteria (natural prebiotics). Whole grains, legumes, fruits and vegetables directly nourish the microbiota.
- ●Fermented foods: yogurt, kefir, sauerkraut, kimchi, tempeh, provide live bacteria (probiotics) which enrich the microbiota. Their association with physical exercise is synergistic.
- ●Avoid unnecessary antibiotics: Antibiotics massively destroy the microbiota, an effect that can persist for several years. Physical activity accelerates microbiotic restoration after antibiotic therapy.
A health check-up allows you to evaluate markers of intestinal and metabolic health and to identify the most relevant lifestyle, physical activity and diet adjustments for your profile. 14px;font-weight:700;color:#006064;font-size:1.1rem">💡 Tips to remember
- Athletes have significantly higher microbiotic diversity than sedentary, with higher levels of bacteria associated with metabolic health and chronic disease prevention.
- Positive changes in the microbiota are measurable after just 6 weeks of regular exercise, even in people who were completely sedentary to begin with.
- 150 minutes of moderate activity per week is enough to produce beneficial microbiotic changes. Regular moderate exercise is more effective than episodic intense effort.
- The gut-brain-muscle axis is a major discovery: the microbiota influences sports performance, mood and cognition, and exercise in turn influences the composition of the microbiota.
- A health check-up allows you to assess markers of intestinal and metabolic health, and to guide you towards the most relevant physical activity and diet adjustments.
