It's basically your liver (and kidneys) pushing glucose into your bloodstream when you wake up. It's common across nearly all animals. It seems like if your body gets used to not having food first thing, the morning response becomes stronger, and your body takes longer to shift to glucolysis. Which might explain the nausea part if you aren't used to eating first thing.

I stopped eating breakfast when I left home, so I'm pretty locked in to 2 or even 1 meal a day since I can't be arsed to waste time eating at lunchtime most days anyway. I make up for it with coffee.