For those of us with auto-immune conditions that can cause “brain fog” like AS/RA etc. quite the opposite. I find the mental sharpness which appears at about 18 hours onwards is brilliant. I look forward to it.
My first fast was interesting… Basically I wait after exam don’t risk it. First couple days I was off in thought and foggy. Third day I actually felt amazing. But when I finally ate again I had the fasting runs and weirdly needed to sleep like crazy
When I did OMAD for about 3 months, mostly salads, meat, few bread/pasta carbs but nothing special I lost 32 lbs and had much clearer thinking, more energy and my sleep was better. Evidently different for everyone…. Go figure.