What Is Runner’s Stomach And How To Avoid It!
I got runner’s stomach really badly last month - to the point where I thought I might not make it to the toilet in time! If you’ve ever been there, you know how unpleasant it is!
Luckily it was just on a training run, but it really made me think about what could have triggered it, and how I can avoid it in the future.
Runner’s stomach, or runner’s diarrhea (or even runner’s trots!) is a curse all endurance runners will face at some point. I’m literally a sports nutritionist, so I’m pretty well versed on how to avoid stomach pain when running…and I still fell victim to it!
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What is runner’s stomach?
If you’re new to this and haven’t gathered from my rather self-exposing introduction, it is a term used to refer to the many forms of gi distress you can experience when running long distances.
This can take the form of cramps, diarrhea, lower abdominal pain while running, upper abdominal pain while running, nausea, vomiting etc.
It’s not fun at all, but it can be avoided or at least heavily mitigated. I’m going to talk you through common mistakes and simple solutions, so you don’t have to suffer through upset stomach runs again!
Why does my stomach hurt when I run?
Runner’s diarrhea is primarily a digestive issue.
It is important to eat lots (and well!) when you are training for an endurance event. However, the combination of hard exercise whilst your body is trying to digest food can trigger GI distress, as your body struggles to do both at once.
This results in the symptoms described above. Not fun!
Why did I get runner’s stomach?
I’m going to take myself as a case study for what NOT to do. Let’s set the scene for last month’s fateful run and figure out what I should have done differently!
I was training for a triathlon at the time, so I was doing a few hours of exercise most days.
The day before I had done a lot of training. This meant I was already conscious of making sure I ate enough to replace the calories burnt during training. At this point in time, I needed to consume around 6000 calories per day.
It’s so important to match your calorie needs… But it can be difficult when running is involved!
On the day itself I did a 3 hour bike session in the morning which consisted of some long hard efforts. I fuelled well on the bike but I still needed to replace some of the calories I had expended.
For lunch, my friend and I had some veggie hotdogs with a nice salad and then enjoyed an ice cream in the sun.
A couple of hours later I had a snack of honey on toast, as I had a 90 minute run planned with some intervals in. This is my usual pre-run snack.
It was during that 90 minute run that my bowels gave up on me and I ended the day on the toilet in considerable distress!
How to stop runner’s diarrhea?
Looking at this scenario, what could I have done differently to avoid getting these symptoms?
The problems were food and timing! There are 3 nutrients which are slow and difficult to digest: fibre, fat and protein.
My lunch had a lot of all 3.
While they're really important in your diet, they can be troublesome for runners because of how long they take to digest.
If you go running before your food has properly broken down in your stomach, you're far more likely to get stomach upset. The mechanical nature of running literally bounces all that food around and starts shifting it through your gut. It'll also cause lots of wind and bloating too!
The other problem here is that any sort of exercise will also decrease the amount of blood flow to your gut, because that blood is being sent to your muscles.
So the digestive process will be even slower than normal.
Even though my honey on toast snack is usually my pre-run go-to, eating it on top of my big lunch meant that it just put another digestive burden on my body. Recipe for disaster!
I go into a lot of detail on what to eat while training for a half marathon or triathlon here, check them out!
Other causes of runner’s diarrhea could be dehydration, underfueling, the use of supplements such as gels or bicarb that don’t agree with you. It could even be posture (if you’re a triathlete, spending a lot of time hunched over a bike can then cause lower abdominal pain while running).
What would I do differently?
Eat a different meal
The most obvious thing to do differently would have been to eat a lower fibre, lower fat, lower protein meal.
Cutting down the salad and reducing oil and cheese would have made my lunch a lot easier to digest.
Or I could have gone for a meal of easily absorbable carbs like white bread or pasta with a lean protein source. Not as fun or exciting and not full of nutritious value, but since my priority was my run it would have been a reasonable choice.
Learn more about carb loading and digestion here.
Eat a smaller lunch
I also could have eaten less, however this doesn’t solve the issue of getting enough calories during training.
One way to resolve the calories issue would have been to drink a high glycaemic index drink immediately after my bike ride.
If I had chosen something with around 70g of carbs in, like maltodextrin or a banana smoothie with honey and blended oats, this would have given me a whack of easy carbs and calories to start replacing what I had burned.
This way, I could have easily eaten less at lunch time.
Skipped the pre-run snack
I also could have skipped the snack before I went running. The snack I had is my normal pre-run snack in the morning and I know I tolerate it well, but on top of everything else I obviously didn't this time.
Although skipping this means I would have been in more of a calorie deficit it would have meant I'd have ran better, had a more productive session and then been able to fuel up properly afterwards.
Alternatively, if I did that that way then I could have taken a couple of gels on a running belt with me for the run, as an easy source of digestible carbs for more calories.
Runner’s Stomach FAQs
How do you fix a runner's stomach?
You can fix a runner’s stomach by being careful with what you eat before you run. Stick to low fibre, low fat and low protein food, as these are harder to digest. Try out different foods to see what causes symptoms and what doesn’t.
What causes runner’s stomach?
Runner’s stomach is caused by undigested food in the stomach and gut being disturbed when you exercise. The fact that less blood goes to the gut while you run slows down the digestive process even more, exacerbating the situation.
How long does runner’s stomach last?
Runner’s stomach will typically begin about 15 minutes into your workout and may last for some hours after. It shouldn’t last more than 24 hours.
Do runners have stomach issues?
Many runners experience stomach issues when running long distances/doing hard training after having eaten. These stomach issues can be avoided by choosing your pre-run meals wisely.
Conclusion: how to avoid runner’s stomach
There you have it! Those are my takeaways from my experience of runner’s stomach symptoms.
While we know that what causes runner’s diarrhea is usually food related, everyone has different trigger foods and foods they can tolerate.
So while I can’t give a one size fits all solution to runner’s stomach, if you are wondering why do I feel sick after running, I would encourage you to look at what you are eating and how much!
Trial some changes, see what works! Good luck!
