I have noticed that my mind is much clearer when I am hungry. Absolutely no brain fog.
In fact, when I was younger, my work crowd use to refer to the carbohydrate hangover that came from eating pasta and other delicious high carb foods. Folks were drowsy at work the day after eating a big Italian meal the night before.
None of that when fasting.
When my son was doing cross country the coach would make the team eat pasta and take ice baths the night before a meet.