What Is Runner’s Stomach?
Causes, Symptoms & How to Avoid It on Race Day
It’s not talked about much…
But almost every runner has experienced it at some point.
👉 Runner’s stomach.
Cramps. Urgency. Discomfort.
Sometimes at the worst possible moment—mid-run or mid-race.
The good news?
👉 It’s common.
👉 It’s manageable.
👉 And in most cases, it’s preventable.
What Is Runner’s Stomach?
Runner’s stomach is a general term for:
👉 Gastrointestinal (GI) discomfort during or after running
This can include:
Stomach cramps
Bloating
Nausea
Diarrhoea
Sudden urgency
It can be mild… or enough to completely disrupt your run.
Why Does It Happen?
There’s rarely one single cause, it’s usually a mix of factors:
🏃 Reduced Blood Flow to the Gut
When you run, your body prioritises:
👉 Muscles over digestion
Blood is redirected away from your digestive system, which can lead to:
Slower digestion
Irritation
Discomfort
🍽️ Eating Too Close to Your Run
Food that hasn’t fully digested can cause issues.
Especially:
Large meals
High-fat foods
High-fibre foods
👉 These take longer to process and are more likely to cause problems mid-run.
💥 Impact of Running
Running involves constant impact.
👉 That repeated movement can physically irritate the gut
This is why it’s less common in lower-impact sports like cycling.
😬 Nerves & Stress
Pre-race nerves can:
👉 Speed up digestion
Leading to:
Urgency
Stomach upset
Common Triggers to Watch
Everyone is different, but common triggers include:
High-fibre foods before running
Fatty or heavy meals
Dairy (for some people)
New or untested gels
Too much caffeine
👉 The key is identifying what affects you.
How to Prevent Runner’s Stomach
This is where you can take control.
⏱️ Get Your Meal Timing Right
👉 Aim to eat 2–3 hours before running
For shorter runs:
A lighter snack 60–90 minutes before can work
🍞 Keep Pre-Run Food Simple
Stick to:
Lower fibre
Lower fat
Easy-to-digest carbs
👉 Save experimentation for training, not race day.
🧪 Practise Your Nutrition
If you’re using:
Gels
Sports drinks
👉 Test them in training first
This is one of the biggest mistakes runners make.
At Coached FITT, we often use products from HIGH5 Sports Nutrition with clients, as they’re simple, effective, and easy to tolerate, but the key point is this:
👉 Whatever you use, practise it before race day.
Your gut needs to adapt just like your training does.
💧 Hydration: Sip, Don’t Glug
It’s not just what you drink, it’s how you drink it.
👉 Drinking large amounts quickly (“glugging”) can:
Cause bloating
Lead to stomach sloshing
Increase discomfort mid-run
A better approach:
👉 Sip fluids little and often
This supports:
Better absorption
More comfort
Consistent hydration
⚡ Don’t Ignore Electrolytes
When you sweat, you don’t just lose water.
👉 You lose electrolytes (especially sodium)
Low electrolyte levels can contribute to:
Cramping
Fatigue
Stomach issues
For longer runs or races:
👉 Consider adding electrolytes to your fluids
Especially in:
Hot weather
Longer sessions
High sweat conditions
🧠 Manage Nerves
Give yourself time before races
Build a routine
Stick to familiar habits
👉 Don’t change everything on race day.
🏃 Train Your Gut
This is often overlooked, but important.
👉 Your gut adapts to what you practise
If you fuel during training:
Your body becomes more tolerant
Symptoms often reduce over time
What If It Happens Mid-Run?
Even with good preparation, it can still happen.
If it does:
Slow your pace
Focus on breathing
Avoid taking in more fuel immediately
Be aware of your route (toilet stops matter)
The Coached FITT Takeaway 🧡
Runner’s stomach isn’t random.
👉 It’s usually the result of:
Poor timing
Food choices
Hydration strategy
Lack of preparation
Get those right, and you reduce the risk massively.
Final Thought
👉 Good performance isn’t just about how you train, it’s about how well you prepare.
Dial in your nutrition, hydration, and routine…
…and your body will work with you, not against you.
Want Help Dialling In Your Training & Nutrition?
At Coached FITT, we help you:
Train smarter
Fuel properly
Perform without guesswork
👉 Send us a message and we’ll help you get it right.