I’m standing at the start line of the North Sea Ultra 111K, my stomach already distended like I’m six months pregnant. My abdomen feels like it’s filled with concrete.
I’m angry that this happened again and wonder how I will make it through this race without going through multiple embarrassing situations.
If I would make it through this race at all.
But at least I would try. Earlier, I debated not starting – but that would be my second DNS (Did Not Start) already this year. And it would be the second because of gut issues.
I decided to risk it and spend the first half of the race anxiously moving from aid station to aid station, trying to hold my urges until I could “go” again.
My gut eventually settled down a bit, and I stopped being afraid of getting myself into disaster pants. However, moving fast was impossible due to the extreme cramps and my swollen belly.
But I finished, and considering the circumstances, I was happy with a 6th-place finish.
My A-race for the first 6 months of the year was 3 weeks later – the German Championships in 24 hours. However, my intestines have once again ruined my plans.
In contrast to the North Sea Ultra 111K, my gut didn’t get better as I moved; it got worse. A lot worse. Eventually, it got so bad that running was impossible because my breathing was restricted, and I couldn’t get any calories down – not even in liquid form.
After a strong start to the race, I felt defeated, sad, and angry when I realized I had to walk the remaining hours. I wanted to throw in the towel.
This wasn’t supposed to be my story in 2025.
Beyond “Runner’s Stomach”: Understanding IBS in Endurance Sports
After sharing my race experiences, the responses are always the same: “Have you tried ginger?” “What about eating bananas?” “Take some white bread.”
The suggestions come from a place of genuine care. Still, they reveal a fundamental misunderstanding of what I’m actually dealing with.
What I experience isn’t typical “runner’s stomach”—it’s Irritable Bowel Syndrome (IBS). This chronic medical condition affects how my digestive system functions every single day, not just during races.
The difference matters enormously because the strategies that work for normal exercise-induced GI distress often make IBS symptoms worse.
What IBS Actually Is
Irritable Bowel Syndrome isn’t just having a “sensitive stomach.” It’s a diagnosed chronic disorder that fundamentally alters how your digestive system responds to normal stimuli. IBS affects the gut-brain connection, making the digestive system hypersensitive to stress, certain foods, and environmental changes.
There are three main subtypes, each creating vastly different challenges:
IBS-D (Diarrhea-predominant): Characterized by frequent loose stools and urgency—the nightmare of sudden bathroom emergencies during races.
IBS-C (Constipation-predominant): My specific subtype involves chronic bloating, distension, and unpredictable bowel movements. Imagine trying to run 100+ kilometers while feeling like you’ve swallowed a bowling ball.
IBS-M (Mixed): Alternating between constipation and diarrhea, making it nearly impossible to predict what your body will do on any given day.
The Critical Difference: Normal Runner GI Issues vs. IBS
Gastrointestinal problems are a common issue in endurance sports. Many runners experience some form of stomach and gut issues during their running career because the physiological stress of endurance running creates a perfect storm for digestive problems: blood flow diverts from your digestive system to working muscles, and the repetitive impact literally bounces your internal organs around, exercise stress hormones alter gut function, and you’re forcing your system to process fuel while under intense physical stress.
For most runners, these factors create occasional discomfort—the kind of thing you power through or laugh about afterward.
But here’s the crucial distinction that many people—including well-meaning coaches and nutritionists—fail to understand: while most runners deal with situational GI distress during races, athletes with IBS are managing a chronic condition that racing stress amplifies exponentially.
It’s the difference between a normally functioning car that occasionally overheats versus driving a car with a faulty cooling system through the desert.
Normal Runner GI Issues:
- Predictable triggers (usually related to specific foods, timing, or intensity)
- Situational (occurs during training/racing but is manageable day-to-day)
- Responsive to standard sports nutrition strategies
- The system returns to baseline quickly after stress ends
IBS + Running:
- Unpredictable triggers (what works Tuesday might fail catastrophically Saturday)
- Chronic baseline (managing symptoms is a daily reality, not just during exercise)
- Paradoxical responses (standard sports nutrition can trigger severe symptoms)
- Amplified stress response (race-day anxiety can trigger the worst flares)
- Cascading effects (one bad reaction can derail performance for hours or days)
For IBS athletes, this might mean living in fear of sudden bathroom emergencies during races, chronic bloating that can make breathing difficult, unpredictable nutrient absorption that makes fueling strategies unreliable, and extreme sensitivity to stress that can trigger severe flares.
Why Standard “Runner’s Stomach” Advice Doesn’t Work
This is why all those well-meaning suggestions often fall short. Ginger might calm exercise-induced nausea, but it won’t address the chronic inflammation and altered gut motility of IBS. Running fasted may prevent food-related cramping in individuals with normal digestive systems, but it can trigger severe constipation flares in IBS-C. Eating easily digestible carbs works great for typical runner GI issues but can cause catastrophic bloating and more for someone with IBS who is particularly sensitive to fructose or gluten.
The advice isn’t wrong—it’s just designed for a different condition entirely. It’s like offering tips for managing a headache to someone having a migraine. Similar symptoms but completely different underlying mechanisms require totally different solutions.
The Mid-Season Pivot: Twenty Years of Diet Experiments Led to a Bold Decision
After the 24-hour disaster, I faced a decision that went against every piece of conventional training wisdom: I decided to completely change my nutrition approach mid-season. But this wasn’t a desperate, random choice—it was the culmination of nearly two decades of systematic dietary experimentation.
My journey through different nutritional approaches started long before I became an ultrarunner.
Since 2005, I’ve methodically tested nearly every dietary philosophy you can imagine: vegan whole foods (2005-2012), strict carnivore/“zero carb” (2012-2015), various low-carb approaches, the Ray Peat/bioenergetic method (starting 2021), and now a return to low-carb, high-fat eating (though not strict keto or carnivore).
Each approach taught me something valuable about my body’s unique responses, building a comprehensive understanding of how different foods affected my digestive system.
But when I transitioned into ultrarunning, I made a critical mistake: I abandoned this hard-won knowledge in favor of conventional sports nutrition wisdom.
Everything I’d been told about ultra-endurance nutrition suggested I should be eating more carbohydrates—it’s practically gospel in our sport. I had been following that advice religiously, increasing my carb intake because that’s what successful ultrarunners do.
The magazines, the podcasts, the elite athletes—everyone preached the same message: more carbs, more fuel, more performance.
Especially recently, where coaches and athletes alike praise the “carb-revolution” for being the driver of the enormous performance breakthroughs in ultrarunning.
So, I, too, adopted a higher-carb meal plan and tried to “train my gut” to absorb more fuel during training. However, the higher-carb approach that should have been fueling better performances was systematically destroying my races, one swollen belly at a time.
So, with several key races still on my calendar, I made a choice that would make most sports nutritionists cringe: I threw out the textbook and went back to what my body was actually telling me it needed.
Building My Personal Fuel Map
One week after the 24-hour race, I am reverting to a higher-fat, lower-fiber approach that has served me well in the past, building my daily nutrition around foods that prioritize energy density while minimizing digestive bulk. Contrary to what I’d been told about fats slowing digestion, these actually seemed to improve my gut motility, and fiber seems to slow it down.
Here’s what I’m doing:
Coconut products are my foundation—coconut oil, coconut butter, unsweetened coconut flakes. These work exceptionally well for my system, providing steady energy without the digestive chaos.
Quality fats like olives, avocados, nuts, and seeds in small amounts.
Minimal (raw) vegetables. This was perhaps the most difficult mental adjustment. Except for tomatoes and cucumber, I will focus mainly on cooked vegetables. Raw leafy greens and big salads leave me bloated.
Simple sugars —honey, fruit purees, and dried fruits for high energy density without the bulk that whole fruits can create. Plus, selected whole fruit that doesn’t cause issues (bananas, oranges).
This approach is the opposite of the high-carb advice that dominates the field of ultra-endurance nutrition. But this is my plan moving forward so that I can race again without every race being a survival mission.
But What About the Low FODMAP Diet?
At this point, anyone familiar with IBS treatment is probably wondering: “What about the low FODMAP diet? Isn’t that the gold standard?”
The low FODMAP diet is indeed the most widely recommended treatment for IBS. FODMAP stands for Fermentable Oligosaccharides, Disaccharides, Monosaccharides, and Polyols—essentially, certain types of carbohydrates that can ferment in the gut and trigger IBS symptoms. The diet involves eliminating high-FODMAP foods for several weeks, then systematically reintroducing them to identify personal triggers.
Research indicates that approximately 75% of people with IBS experience improvement on a low-FODMAP diet, making it the current gold standard treatment. It’s evidence-based, well-studied, and has helped millions of people manage their symptoms.
But here’s what the research also shows: 25% of people with IBS don’t benefit from FODMAP elimination—and some might actually get worse. I appear to be in that minority.
My approach is actually more restrictive than low FODMAP in many ways. White bread and white rice are considered low-FODMAP foods, but they trigger severe symptoms for me. Many vegetables that are FODMAP-friendly cause me digestive distress.
On the other hand, I can include certain foods that are considered a “no” on the low FODMAP diet. For example, dried dates and apples—both high in FODMAPs—work perfectly for my system (in small amounts).
Low FODMAP Versus Low-Carb: Understanding the Mechanisms
Both diet approaches work to ease IBS symptoms, but through different mechanisms:
Low FODMAP Diet:
- Works by reducing fermentable carbohydrates that can trigger gas, bloating, and other IBS symptoms
- Requires a complex elimination and reintroduction process
- Gold standard treatment backed by extensive research
Low-Carb Approach:
- May alter gut microbiota by reducing carbohydrates available for fermentation, favoring bacteria that metabolize proteins and fats
- Simpler to implement than FODMAP elimination
- Can be more sustainable long-term for some people
- Particularly beneficial for those who don’t respond well to FODMAP restriction
Why Individual Testing Still Matters
Here’s the crucial insight from both the research and my personal experience: research is needed to enable personalized treatment strategies. While we now know that both approaches can be highly effective, we still can’t predict which individual will respond better to which approach.
My food tolerance map perfectly illustrates this unpredictability:
- High-FODMAP foods that work for me: Dates, apples, mangoes (all in small amounts)
- Low-FODMAP foods that cause problems: Many vegetables, certain grains
- Low-carb foods that work perfectly: Coconut products, quality fats, Tofu, Tempeh
- “Safe” carbs that don’t work: White rice, potatoes (contrary to most advice)
This pattern doesn’t fit neatly into either dietary camp, but it’s my reality. And that’s precisely why systematic individual testing remains essential, regardless of what the population studies show.T
The Practical Implications for Athletes
For endurance athletes with IBS, this research offers both validation and direction:
- Both approaches are legitimate first-line treatments—you’re not limited to just trying FODMAP elimination
- Dietary interventions consistently outperform medications for symptom management
- Long-term sustainability matters—the approach you can stick with is the one that will work
- Individual variation is enormous—what works for other athletes with IBS might not work for you
The key is developing a systematic approach to testing what works for your unique digestive system rather than blindly following population-based recommendations.
I prefer to return to a low-carb, high-fat diet because I know it has worked for me in the past, and it is easier to manage in day-to-day life. I already know which foods work for me and I don’t need to consult a list of foods to see if what I want to eat is low or high FODMAP.
AI-Driven Individualized Approaches: The Future of IBS Management
The concept of truly personalized nutrition for IBS is rapidly evolving beyond simple elimination diets. Recent groundbreaking research has demonstrated that artificial intelligence can analyze individual gut microbiome profiles to create personalized dietary recommendations. This approach aligns perfectly with my personal experience of needing individualized solutions.
A landmark 2024 multicenter randomized controlled trial published in the American Journal of Gastroenterology compared AI-assisted personalized diets with the standard low-FODMAP approach in 121 patients with IBS.
The results were remarkable: while both approaches showed significant symptom improvements, the AI-driven personalized diet demonstrated superior outcomes across multiple IBS subtypes and achieved something the FODMAP diet couldn’t—it actually improved gut microbiome diversity rather than potentially compromising it.
Here’s how the AI approach works: researchers analyze an individual’s gut microbiome composition and use machine learning algorithms to predict which specific foods will promote the growth of beneficial bacteria while reducing the growth of harmful microbes.
The system scores approximately 300 foods on a scale of 0-10 based on their predicted impact on that person’s unique microbiome. Foods scoring 8-10 become dietary foundations, 4-7 are included for variety, and 0-3 are avoided.
What makes this approach particularly compelling is that it addresses the fundamental limitation of population-based dietary advice.
The study found that the AI-recommended diets had only a 29% overlap with FODMAP diets—meaning 71% of the recommendations were utterly different. This explains why some of us don’t respond well to standard approaches: we’re not getting the right advice for our individual gut ecosystem.
This research validates what I’ve learned through two decades of self-experimentation: the future of IBS management lies not in one-size-fits-all approaches but in understanding and working with our individual biological systems.
While AI-driven personalized nutrition isn’t yet widely available, it represents the logical evolution of the systematic testing approach I’ve been implementing.
The Finish Line is Personal: Thriving with IBS in Endurance Sports
For fellow endurance athletes struggling with IBS, I want to offer this: you don’t have to choose between your sport and your gut health. You don’t have to accept that every race will be a survival mission or that DNFs due to digestive disasters are just part of your story. However, you must be willing to question conventional advice and do the patient work of determining what actually works for your unique system.
The future of IBS management is moving toward true personalization—whether through advanced microbiome analysis, AI-driven recommendations, or simply more effective frameworks for individual testing. Until those tools are widely available, we have the power to become our own best advocates and researchers.
My next big race is CCC UTMB in 11 weeks. And I plan to approach it without dread about my gut betraying me mid-race. Instead, I’m excited to see what my body can actually do when it’s properly fueled rather than fighting against my nutrition choices.
While I don’t believe that my concrete-belly days are completely behind me—IBS is a chronic condition that requires ongoing management – I trust that focusing on gut health will lead to more enjoyable Running (and races) again. I decided to fuel myself with something that works with my body rather than against it.
I will be listening to my own body again, respecting its unique needs, and having the courage to forge my own path—even when it goes against everything the textbooks say an ultrarunner should be doing.
Sometimes, the best performance strategy is the one that acknowledges your limitations and builds around them rather than trying to force your body into someone else’s template for success.