Hi D.,
My son is a distance runner and my husband also runs a lot, although not marathons. You have a form of irritable bowel syndrome, which can manifest as constipation, diarrhea, or a combination of both. It can flare up during various times of stress - in your case, it appears to be exercise. But the exercise isn't causing it - you already have the problem. Given that the race is in a few weeks, you really don't have a lot of time to fool around with dietary changes and hope that they work, particularly because you will be in another country and experiencing new foods (even if you ate them when you lived in Europe). I have several friends with IBS, including one who is a track coach, and they have had great results with Reliv products, particularly the dietary supplement. One friend got rid of his IBS in 2 days, others might take a few weeks. I'd be happy to help you. I don't live all that far from you either so we can even meet so I can show you more. Let me know. You also cannot run a race of this sort without eating the day before, believe me - and one day without food won't solve the problem anyway - it's more a question of getting your colon and digestive system healthy. We can do that by working together. If you would like to talk to my friend the track coach & phys ed professional, I can arrange that too.