Kind of coincidence to find this thread.
I also under-fueled my first (solo) 50k and bonked heavily.
Had mis-calculated my carb intake and only ate about 1 gel (Maurten 100, Spring Energy) per hr. So I hit a wall at around 36k in. I never had such cramps before, for a while I couldn’t even walk slowly. Took a rest in the shadow, ate, drank, waited …
The last 15k distance/500m vert I could only hike. Running wasn’t even a wish anymore. Just getting it done.
Now I looked up things again and found that I maybe only consumed around 50% or less of the needed carbs.
On next saturday I have my 2nd 50, now supported. So there will be aid stations = carbs! 😉 I plan to take plenty of gels with me (Maurten 160 gels), set a eat/drink reminder on my watch and get fueling right from the start. We’ll see if I will be able to tolerate the increased input.