The Unlikely Reason a Crohn’s Patient Started Running Marathons
The Long Run Mindset - For a Life Worth Living #21
Three months after a surgeon removed a metre of my intestines I went for a run.
I have no idea what I was thinking.
The Book That Started It
I’d been reading about running. Nothing specific — one of those comprehensive guides that covers everything from first steps to marathon training. The kind of book you buy when you’re not yet a runner but you’re thinking about becoming one.
Somewhere in the middle of it I read something that stopped me.
Long distance running, it said, suppresses the immune system. Particularly in the weeks building up to a marathon. Runners need to be careful — a cold, an infection, anything that puts the immune system under additional stress could derail months of training and ruin race day.
I put the book down.
I picked it back up.
I read it again.
Now I want to be completely clear about something. I have no scientific evidence for what I’m about to tell you. No doctor suggested it. No study confirmed it. What I had was a theory, formed in a quiet room by a man who had just had a metre of his intestines removed and was trying to find a reason to believe things could be different.
Crohn’s disease is, at its core, an overactive immune system attacking the digestive tract.
Running suppresses the immune system.
Therefore —
It was the most unscientific logic I have ever applied to anything in my life. It was also the logic that changed everything.
The First Run
About three months after the resection I laced up a pair of trainers and went out.
The canal was flat. I picked it deliberately — no hills, no excuses, nothing to negotiate with. Just a path alongside water and whatever I had left in a body that had been through a great deal.
Forty five minutes. Roughly 5k. I felt awful by the end.
I went home, lay on the sofa, and didn’t run again for a week.
It took that long to recover.
The following week I went again. Forty five minutes. Canal. Felt awful. Went home.
Once a week. That was the whole programme. No app, no coach, no plan. Just one run a week, feeling rough afterwards, going back anyway.
I want to be honest about why I kept going in those early weeks. It wasn’t joy. It wasn’t a runner’s high. It was the theory. The stubborn, unscientific, completely unverifiable belief that I was doing something to my immune system that might — might — mean I never ended up back on that operating table.
Sometimes belief is enough to make you act. Even when the evidence is thin.
If you’re finding this interesting you can get The Long Run Mindset in your inbox every Tuesday — free. Subscribe below.
The Day It Changed
A few months in, on a warm day, I ran 10k along the canal.
I don’t know why that day was different. The same path, the same trainers, the same body that had been shuffling through these sessions for months.
But somewhere around the 8k mark something shifted. The effort stopped feeling like punishment and started feeling like something else entirely. Something I don’t have a precise word for.
I got back home shaking. Not the usual post-run tiredness — proper shaking, the kind that comes when your body has done something it didn’t know it could do. I went to bed to warm up and recover.
And lying there, still shaking, I got my phone out and signed up for the Burnley 10k.
But here’s the rule I created that day — almost without realising it.
Before I finished one challenge I would sign up for the next one.
Not after. Before. While I was still in it, still uncertain, still finding out what I was capable of. Before I crossed that line I needed to know there was another line waiting.
So before the Burnley 10k I signed up for a half marathon. Before the half marathon I signed up for Chester. And before Chester — before I’d even stood on that start line — I’d already entered a marathon in January.
Chester. Four Hours, Forty Three Minutes, Forty Seconds.
Eighteen months after the resection I stood on the start line of the Chester Marathon.
I won’t pretend I knew what I was doing. I’d followed a plan, done the long runs, trusted the process in the way that first time marathoners trust the process — with slightly more hope than certainty.
Mile 25. Cramp. The kind that arrives without warning and makes every remaining step a negotiation.
I kept going. What else do you do at mile 25?
And then something strange happened.
The final stretch of the Chester Marathon finishes on a racecourse. Proper turf. And after 25 miles of tarmac the ground felt — springy. Alive. Like running on a completely different surface.
My legs were drunk. That’s the only way I can describe it. I thought I was sprinting for the line. I probably looked like I was moving in slow motion. But in my head I was flying.
Four hours, forty three minutes, forty seconds.
Eighteen months earlier I couldn’t run for forty five minutes without spending a week recovering.
I cried. Of course I did.
The next year I ran twelve marathons in twelve months. Including my first ultra.
The rule was working.
Where the Rule Gets Tested
The thing about always setting the next challenge before you finish the current one is that the challenges keep getting bigger.
Twelve marathons became ultras. Ultras became hundreds. Last summer I ran the Spine Challenger South — 113 miles along one of Britain’s most demanding trails.
Up until that point I had always run the full distance in training. Always. Which meant I always knew, with certainty, that I would finish. I’d already done it. Race day was confirmation, not discovery.
The Spine Challenger changed that. 113 miles is not something you run in training. For the first time in my running life I genuinely didn’t know if I would finish.
I did. But it was different. The certainty was gone.
This year it’s the Leeds to Liverpool Canal Race. 130 miles. Two days of non-stop running along the same waterway where I once shuffled a 5k and spent a week recovering.
I still don’t know if I’ll finish.
And for the first time I’m considering breaking my own rule — not setting the next challenge until after. Because if I don’t finish I’ll be back next year. And sometimes the most powerful thing you can tell yourself at mile 90, when everything hurts and stopping feels entirely reasonable, is this:
If you give up now you have to go through all this again just to get back to this point.
That’s not a threat. That’s a strategy.
Maybe after LLCR the next challenge looks different entirely. Seven marathons in seven days. Twelve 50ks in twelve months. Something that tests a different kind of endurance.
I genuinely don’t know yet.
And for the first time in over ten years of running, not knowing feels like exactly the right place to be.
What I Know Now
I still have no scientific evidence for my immune system theory.
My consultant has never endorsed it. No study has confirmed it. It remains exactly what it was on the day I formed it — a theory, built from logic and desperation, by a man who needed a reason to put his trainers on.
But here is what I do know.
I haven’t had a Crohn’s flare-up in over a decade.
I run every day. Not because a streak demands it — I got past that — because it’s who I am now.
Maybe the theory is right. Maybe it’s coincidence. Maybe the diet, the stress, the whole changed life is what made the difference and the running is just the part I can measure.
I don’t need to know which one it is.
I just need to keep putting my trainers on.
Thanks for reading The Long Run Mindset! This post is public so feel free to share it.
If you’ve enjoyed this and not yet subscribed, the best thing you can do to help is hit the button below — it’s free and only takes ten seconds and it means the world.
Another interesting read Andy. Got to go with your instincts and stick to them. You don’t need scientific proof for something that clearly works for you