re: IF and exhaustive afternoons

Glucometers are cheap, buy one and measure your glucose and remove that question from your mind altogether. (Because it's probably not low sugar, but a glucometer isn't a bad thing to have around, just for these situations when you have questions about "What is my blood sugar?" and you can prick your finger and know in seconds)

But ....I don't think it's abnormal for a human to feel sleepy at that time....I think it's absolutely normal, and the only tweak should be you learning to power-nap for 15-20 in the afternoon.