Maybe low blood sugar. You're not doing anything stupid, are you?
If I do a lot of workout volume, I'll have a "hangover" that can last a few days. The worst of all is the deadlift hangover. I'm physically tired and sore, of course, and I nap. What I wonder about most is why my brain is so foggy. Analytical thinking is much more difficult and I have to work much harder mentally to read technical documents. What's the biochemistry of this brain fog?
Maybe low blood sugar. You're not doing anything stupid, are you?
What's your age? I had similar symptoms (every day) that were much worse after a grueling squat/dead day...especially the brain fog. Low T was the culprit. No issues other than normal recovery since starting TRT.
I'm assuming your diet and sleep are on point.
Do you have sleep apnea?
Internet diagnosis is best diagnosis.
I keep my carb intake low and after some years of doing it I have mostly found the balance I can tolerate well. On the occasions I tried Atkins, I got brain-busting headaches as I got into ketosis. No more of that for me. I don't crave carbs in the sense I feel I have to have them or I feel deprived. But when I don't get enough, I get foggy as you described it. I seem to recall reading that the brain cells need two times more energy than the other cells in your body. So maybe more carbs are your answer.
41 years old. 6'5". 183 lbs. Rip has referred to me as an insect in the past due to my lean physique. I'm a rock climber for 20+ years. Rightly or wrongly, climbers are worried about increased weight. I suppose I'm an experimental climber who has budgeted a 10 pound gain for barbell training thinking it will help with climbing. I think it has.
I sleep plenty. 8-10 hours is usual. I don't usually fall asleep after dinner but on these hangover days, I do crash at some time in the afternoon or evening. Last night it was at 7 pm for an hour.
I do eat real food (meat, fruit, and vegetables) especially after a volume workout. I didn't let myself be hungry at any time. Possibly force feeding myself more would be a solution.
There are diabetes issues in the family and I've been tested but always negative.
OP, my hangover usually lasts about two to three hours. Perhaps your low bodyweight is contributing to the longer hangover? (I'm 5'8" (173 cm), 199 freedom units.)
I used to think my hangover was valsalva related, but after reading this post and thinking, "Bro, you're not alone," I did a quick bit of googling, which of course now makes me an expert. /s
It seems the brain accounts for something like 20% of the body's energy expenditure. (I assume that value is for normal, relatively-sedentary humans.) I found this blog post about glucose/glycogen depletion quite interesting even though it discusses rats and running. The curve showing brain glycogen depletion, recovery, and supercompensation seems like a good explanation for my ~ three-hour post-workout hangovers.
I've experienced the same issue. It abated somewhat after I started taking longer breaks between reps and mixing in the occasional extra rest day. I still get a hangover occasionally, but it no longer lasts multiple days. And the hangovers are less severe and don't prevent me from ostensibly normal functioning.