Depends if you’re getting enough sleep or not I guess, and when your feeding window is, I personally eat in the morning, maybe an hour after I wake up and I do not feel tired afterwards.
I tend to feel tired when I do an Extended Fast & when I eat a lot on refeed.
Something’s wrong here. What’s your diet like? Are you hydrating correctly? Do you feel like this when you don’t fast?
I’d be tempted to talk to a medical professional. Could be signs of an underlying condition.