Nutrition
I get asked questions about nutrition all the time. My response is to eat foods running as close to what you normally eat every day as this should greatly reduce gut issues. I know you can't carry those foods with you without some serious issues, but you can get real close with a few small adjustments. I've figured out two different approaches to get real food while running in any setting. One is to make some simple foods that I can easily carry and the other is to get some stuff prepackaged that is real food.
What I make are what a friend calls bullet burritos. These are a combination of rice and refried beans flavored how you like and placed in some sort of bread. I use black beans and whatever rice is handy tucked into a Flatout Foldable, these are more bready than tortillas and just as easy to use. I do everything from scratch and the pictures give you an idea of the order I do it all in; but one key I've learned is to fry them after they have been made and allow them to cool completely before bagging them up, the reason for this is that it keeps the bread from getting soggy.
A shameless plug here for Spring Energy. When I'm eating enough of these they are simply the best bar none. Real food and I've never had stomach issues unless I'm eating something from an aid station something that I don't normally eat. I just have to have enough of them on hand otherwise it's as if I had eaten something I don't normally eat. I get the same discount everyone else gets, so use the code 'JackS' at check out. If you're not sure if you would like them or not try the sample pack. My personal favorites are the SpeedNuts, Koffee, Power Rush and Long Haul.
I also tell folks to eat every 20 to 30 minutes whether it’s a training run or a race, getting behind on nutrition/calories makes it really hard to get back to even. The farther I go on a run the more frequently I eat as time goes on, while eating smaller bites, so I'm taking in the same calories over the same amount of time just at maybe a 10 minute interval. This has kept me from getting behind on calories when I'm not really in the mood to eat.
When I did SCAR southbound in the summer of 2017 I learned I need variety of foods. When I DNFed the Pinhoti 100 in fall of 2018 I learned I have to know what the aid stations will and more importantly what they will not have to eat. These efforts have served as great guide posts for me as to how I should eat while running.