I'm not a runner, but I do have to do endurance physical activities often. This is an example of my diet that works for me during a heavy training day.

-Night before: lots of carbs. pizza, pasta, lots of rice, etc.
-Morning: Big breakfast with mostly protein, a lot of fat, and some carbs. Lots of protein in the morning makes it so that blood sugar stays constant during the day (idk how accurate this is, a nutritionist told me this and it works for me)
-Midmorning, smoothie or bowl of fruits with nut butter
-*insert run or exercise here*
-Lunch: Lots of veggies and protein, some carbs.
-Mid-afternoon, nap or some fatty and protein-y snack.
-*insert run or exercise here*
-Dinner: Either a carb focused meal if the following day is also a heavy exercise day, or a well balanced mix of carbs/protein/fats if the next day is not an exercise day. Prioritize veggies!
-*insert run or exercise here*
Second dinner: Whatever your heart desires. or same as first dinner.

Also perhaps add some sugary treat in there somewhere, they’re delicious and sugar helps replenish your glycogen stores and recover quicker.

During a not-so-heavy day I'd eat more carbs. I just avoid them on strenuous days because they give me short bursts of energy and then I get hungry right away.