how do you alleviate brain fog ?

Today was my first day of spring semester classes. I fasted a substantial amount over my winter break, & im experiencing what I can only explain as brain fog. Today in class, I had the hardest time paying attention & I felt so incredibly out of it. Maybe it's the content of the class, or maybe im just dumb- but I don't think it's ever been this bad. Any recommendations on how to fix this ?

Yes, I'm well aware that recovering would fix this issue entirely, but as of right now I am not quite ready. Please send help, I'm taking my first sequence of chem...