Any gastrointestinal symptom can cause a surprising degree of interference when you run.
Whether you are nauseous, gassy, or have diarrhea or constipation, if your GI system is causing some detectable symptom, it can throw your workout off.
Runner’s stomach is a common issue that causes problems such as bloating, nausea, diarrhea, and stomach cramps when running.
As a running and nutrition coach, I see these issues in many of my athletes, and we work to set up a specific fueling plan for each.
In this guide, we will discuss runner’s stomach or runner’s gut, its most common causes, and how you can treat and prevent it so it doesn’t affect your runs.
What Is Runner’s Stomach?
Runner’s stomach may also be referred to as runner’s belly, runner’s tummy, and runner’s trots.
It is a loose term that describes various gastrointestinal symptoms while running, such as abdominal pain, cramping, nausea, diarrhea, gas, bloating, an upset stomach, the urgency to use the bathroom, belching, and side stitches.
You may also experience stomach pain after running.
Experts suggest1ter Steege, R. W. F., & Kolkman, J. J. (2012). Review article: the pathophysiology and management of gastrointestinal symptoms during physical exercise, and the role of splanchnic blood flow. Alimentary Pharmacology & Therapeutics, 35(5), 516–528. https://doi.org/10.1111/j.1365-2036.2011.04980.x that runner’s stomach can be caused by the actual jostling and mechanics of the running motion, as well as dietary, hydration, training, and hormonal factors.
Studies have found2Samborski, P., Chmielarz-Czarnocińska, A., & Grzymisławski, M. (2013). Exercise-induced vomiting. Przegla̜d Gastroenterologiczny, 8(6), 396–400. https://doi.org/10.5114/pg.2013.39924 that up to 83% of marathon runners have gastrointestinal complaints associated with their running, including GI distress, runner’s diarrhea, cramping, and other stomach problems.
What Causes Stomach Cramps When Running or Stomach Pain After Running?
There are various causes of runner’s stomach, including the following:
- Not waiting long enough after eating to go running can cause cramps in the stomach when running.
- Drinking sugary beverages and eating high-carbohydrate foods3Morton, D., & Callister, R. (2014). Exercise-Related Transient Abdominal Pain (ETAP). Sports Medicine, 45(1), 23–35. https://doi.org/10.1007/s40279-014-0245-z may increase the risk of stomach cramps while running.
- Dehydration and drinking water too quickly can cause stomach bloating when running.
- Eating fatty foods, high-fiber foods, and high-protein pre-run snacks and meals can delay gastric emptying and can increase bloating when running.
- Running too fast.
- Hyperventilating or breathing with an uneven pattern can cause stress on your diaphragm.4Morton, D., & Callister, R. (2014). Exercise-Related Transient Abdominal Pain (ETAP). Sports Medicine, 45(1), 23–35. https://doi.org/10.1007/s40279-014-0245-z
What Are Effective Strategies For Preventing Runner’s Stomach?
Here are some tips to prevent gastrointestinal distress while running.
#1: Eliminate Foods That Cause Bloating
Many runners suffer from runner’s stomach if they eat foods before running that cause bloating.
There isn’t a definitive list of foods that cause bloating for all people. Certain foods may trigger bloating more than others, depending on your digestive system and personal sensitivities.
For example, if you have lactose intolerance, dairy products can cause a buildup of gas in your intestines and colon, causing abdominal bloating.
That said, certain foods tend to increase gas production for most people, such as foods high in fiber, sugar, or sugar alcohols and foods high in fermentable oligosaccharides, disaccharides, monosaccharides, and polyols (FODMAPs), such as onions, garlic, and cauliflower.
These foods can increase fermentation by the bacteria in your gut, which leads to excessive gas production that will get trapped in your stomach and intestines.
Carbonated beverages, such as soda, seltzer, and beer, contain gaseous carbon dioxide, so drinking any carbonated beverage, especially if you drink it quickly, can lead to temporary belly bloating.
Chewing gum can also increase bloating because it causes you to swallow more air, which gets trapped in your digestive tract.
In terms of bloating caused by water retention, salty foods such as chips, pretzels, deli meats, canned soups, most sauces and condiments, fast food and restaurant dishes, frozen entrées, and pickles, can cause your body to hold onto more water, which can fill your abdomen and result in a distended stomach.
If you would like to develop a specific nutrition plan for your needs, you can work with a registered dietitian who specializes in athletes.
#2: Rethink Your Hydration
Many people get stomach cramps while running because they are dehydrated or they drink plain water too quickly, which causes the water to slosh around in their stomachs as they run.
You need to dial in your hydration needs to prevent stomach cramps while running.
If you’re a heavy sweater, you’re probably all too familiar with soaking through your workout clothes, even though you might be in great shape.
You should determine your sweat rate by weighing yourself before and after a run with no clothes on and then taking the fluid loss as the amount of water weight you lose in sweat during the run.
The reason it is important to take your clothes off is that after your workout, if you do not remove your sweaty clothes, you will not be able to accurately assess how much fluid weight was lost.
You also need to weigh yourself without clothes before the run so to keep the conditions balanced.
For example, imagine that you go for a 60-minute run. Before the run, you weigh 165 pounds (75 kg). After the run, you weigh 164 pounds (74.5 kg).
This means that you have lost 1 pound, or 16 ounces, during your 60-minute run.
Therefore, in the environmental conditions you were running in, your sweat rate is about 16 ounces per hour, which means that you will need to take in that much fluid as you run.
Keep in mind that this method entails not drinking any fluid during your workout. This can be contraindicated in certain circumstances, such as during long-distance runs and when exercising in the heat.
Alternatively, you can consume fluid during the workout, but you will need to be meticulous about measuring the number of ounces of fluid weight you drink so that you can subtract the weight of that liquid volume after your workout.
For example, you can drink 8 ounces, 16 ounces, or even 32 ounces of fluid during your workout and then just subtract that liquid weight from your final weight to determine how much sweat you actually lost.
In our example, if our 165-pound runner had hydrated with 16 ounces of fluid during her run, Her pre-run weight and post-run weight would have been the same, indicating that she hydrated perfectly and that her sweat rate is still the same 16 ounces per hour.
During exercise, it is usually best to take in fluid periodically and gradually so that you do not overload your system with water all at once, which can lead to uncomfortable bloating and sloshing in your stomach and can decrease the absorption rate of your fluids.
Therefore, a good hydration strategy should be planned out for the fluid portion of hydration needed during exercise. For our example subject, they would need to drink about 4 ounces of water5McDermott, B. P., Anderson, S. A., Armstrong, L. E., Casa, D. J., Cheuvront, S. N., Cooper, L., Kenney, W. L., O’Connor, F. G., & Roberts, W. O. (2017). National Athletic Trainers’ Association Position Statement: Fluid Replacement for the Physically Active. Journal of Athletic Training, 52(9), 877–895. https://doi.org/10.4085/1062-6050-52.9.02 every 15 minutes during the run.
On hotter days, this should be adjusted up to 6 ounces or so, depending on the temperature difference between the two conditions.
Consider adding electrolytes and glucose to your water, particularly if your workout exceeds 90 minutes.
Studies have shown6Millard-Stafford, M., Snow, T. K., Jones, M. L., & Suh, H. (2021). The Beverage Hydration Index: Influence of Electrolytes, Carbohydrate and Protein. Nutrients, 13(9), 2933. https://doi.org/10.3390/nu13092933 that drinking plain water causes people to feel more bloated than drinking electrolyte—or carbohydrate-infused beverages.
Plus, there is a large body of evidence7Orrù, S., Imperlini, E., Nigro, E., Alfieri, A., Cevenini, A., Polito, R., Daniele, A., Buono, P., & Mancini, A. (2018). Role of Functional Beverages on Sport Performance and Recovery. Nutrients, 10(10), 1470. https://doi.org/10.3390/nu10101470 that has found that sports drinks that combine carbohydrates (particularly glucose and fructose) with electrolytes can improve athletic performance by optimizing the absorption of water and electrolytes and maintaining metabolism.
According to research, the ideal concentration of carbohydrates in these electrolyte drinks is 6-8%. For workouts lasting over 90 minutes, the overall goal is to ingest 30–80 grams of carbohydrates per hour.
#3: Wait Long Enough After Eating to Run
It’s common to get stomach cramps while running and experience other digestive issues if you run too soon after eating.
Plan to wait about 3-4 hours to run after eating a large meal, 2-3 hours for a small meal, and 1-2 hours after most snacks unless it’s a very small snack consisting of only simple carbohydrates (like a gel) and you’re doing a very low-intensity, slow recovery run.
#4: Slow Your Breathing
Consider a 3:2 breathing pattern, and make sure you are taking slow, deep belly breaths while running.
This involves inhaling for a count of three steps and exhaling for a count of two, so you should inhale for three-foot strikes and exhale for two strikes.
Overall, digestive distress is quite common during running, and you may experience cramps or stomach pain due to issues with the timing and choices of foods you eat before and during running, your hydration strategy, the pacing of your runs, and your breathing patterns.
Identifying the likely causes of your GI symptoms while running will help you most successfully target the issue and make necessary corrections to your dietary and training strategies to prevent stomach issues while running.
If your symptoms don’t subside with our tips, you may need to see your healthcare provider to rule out other issues such as acid reflux, irritable bowel syndrome, irregular bowel movements, and so on.
Ready to carb up? For a list of great pre-run snacks for your workouts or on race day, check out this next guide:
