Because parts of your body must work to digest that food (gut, liver, pancreas, etc). You don’t perceive it, but it’s happening. Then your blood sugar raises,

Because parts of your body must work to digest that food (gut, liver, pancreas, etc). You don’t perceive it, but it’s happening. Then your blood sugar raises, which your body works to bring down. So your body is not resting even though parts of your brain may be.