Perfect example…I did IM Boulder in 2019 and had a great swim and bike. I started the run, feeling really good for about two miles, and then my stomach started cramping. It was all stomach with nothing major happening in my lower GI. At about mile three, I had to stop running completely because I thought I was going to puke and then it was a death march for much of the remaining run. I stopped eating completely hoping I would digest everything in my stomach and then I could resume taking in nutrition but by that point I had lost focus on the race and was in survival mode. I did keep driving water throughout this entire process because I didn’t want to compound the issue with dehydration.