Whenever I have fallen asleep after food I think it has also involved reactive hypoglycaemia as well as high blood glucose.
If you still have the capacity to produce reasonable amounts of insulin AND you eat enough carbs to send your blood glucose high enough, sometimes your body produces too much insulin for the amount of glucose. It is a sort of panicked over reaction by your pancreas. This makes your blood sugar drop sharply, going too low, and ending up with hypoglycaemia.
I used to snooze off on a glow of replete high blood glucose. During my nap, my blood glucose would drop sharply, until I woke up feeling utterly dreadful. Dark, sluggish, depression, headaches, lethargy and apathy. It took a long time to wake up and I felt dopy and sluggish for a long time afterwards.
The answer was to avoid the sharp rise in blood glucose (not eating the carbs), which would trigger the whole miserable cycle.