My experience running was that carbs were not necessary. I ran some 10k races with carb loading and some with low and near zero carbs to experiment. My times did not change much. I was running hard for an older guy, about 40 minutes plus or minus a minute depending on the course, at 40 years age. I found I could train harder and run with less fatigue on low carb than high. Energy levels more stable. With carbs your energy rises and falls as you run. With low carb you run evenly and don't get exhausted. After runs I did crave food. I liked a very high fat meat best, second best was a carb snack like ice cream. Both satisfied the craving. Cream and berries made a great snack after running hard.