How Exercise Affects the Gut
If you are reading this blog post, I’m going to take a wild guess here and say you are no stranger to running with stomach pain. Sometimes it may be sloshing, running into the bushed, cutting your run short because your belly pain is too much, choosing not to eat the next gel on your long run because your stomach can’t handle it anymore then bonking, finishing your run and feeling more bloated that you started… the list goes on! Most runners experience this and it’s complicated! It could be as simple as a food timing issue. You either ate too much right before your run, or you did not eat enough to fuel your run. Both can look and feel the same so it can be hard to pin down sometimes. Or your running has altered your gut, and you are going to have to put in some work to make some gut changes to support your exercise and exercise changes to support your gut.
Food timing. It matters.
It seems simple that you can eat too much, too close to your activity and if you do, you're going to have some stomach pain. BUT it doesn’t seem as obvious that if you do not eat enough before your run to properly fuel your run, you can also get bloating and stomach pain. MIND BLOWING! Your running is fueled by carbohydrate. If you don’t eat enough, you don’t have enough energy. That’s very simple math. But did you know that your gut microbiome also needs carbohydrates to properly digest fuel and provide you with energy?? Yes, that’s right, your entire system needs fuel to keep you running and digesting. Depending on the duration of your activity, you will also need to fuel during your run to keep the gut happy. I recommend eating about 100 calories worth of carbs, or 25 grams of carbs within 30 minutes of exercise and then 20-40 grams of carbs every 30 minutes after that to maintain enough energy to keep running, and a happy gut. If you are running for 60 minutes or less, you don’t need to focus on the intra-run fueling. But certainly anything 1.5 hour or more needs fuel!
If you are an early morning runner, a cookie, banana, or piece of toast will do the job wonderfully. If you run later in the day, the fuel timing can become tricky. In this case, I would aim to finish your previous meal 2 hours prior to your run AND fuel with your carb snack. Avoid protein heavy meals for the meal that proceeds your run as this can slow down digestion and leave your run feeling a bit sluggish.
Carbs can be fun and easy during training!
Aside from the simplicity (it’s not simple, meal timing can feel so complicated, but next to all the other gut stuff, it seems really simple) of meal and snack timing, the intricacies of exercise and gut health can also impair your runs and performance. Here are the basics of connectiveness of gut health and running.
Moderate exercise may support a healthier gut microbiome.
Regular moderate exercise has been associated with greater microbial diversity and changes in the gut microbiota that may support metabolic and immune health. Exercise if important for nearly every aspect of health and someone who partakes in regular exercise will not only have better heart and bone health, but their gut microbiome can be healthier too! So why do so many runners struggle with GI distress? As mentioned above, meal timing is important in fueling the diverse critters in our guts. It’s also important not only for injury, but for our gut health to exercise an appropriate amount for what our unique bodies need.
More exercise isn't always better for the gut.
High-intensity or prolonged endurance exercise can increase gastrointestinal permeability and contribute to GI symptoms. Factors such as heat, dehydration, reduced blood flow to the digestive tract, and high training loads can all play a role. Everybody is different, and you can absolutely train your gut through both diet and exerise to tolerate more intesity or duration, but this is an important factor to keep in mind. Just like your bones can get a stress fracture from too much exercise, your gut can get “fractures” too or become permeable. Gut permeability leads to bloating, gas, and constipation or diarrhea depending on how your body deals with that stress.
Your gut and your training can influence each other.
The relationship appears to be bidirectional: exercise can alter the gut microbiome, while gut microbes may influence processes relevant to athletic performance, including carbohydrate metabolism, inflammation, and production of short-chain fatty acids. However, researchers emphasize that the performance implications are still being investigated.
All this is to say, it’s a complicated dance and it should be determined on an individual scale. If you are stuggling with these things, I’d love to help coach you through this. Check out my TeamRunRun coaching profile HERE, or contact me to see if we would be a good fit for working together!
Me, racing in Slovenia at the Ultra X Word Championships. This was the most beautiful race I have ever done!!!