The best way to think of it is imagine what would happen if you started a fire using wood created from ectoplasm. It would burn for a while, maybe even completely, but once it's time is up it would vanish. The body doesn't burn fuel as rapidly as a fire, so you would feel full for an hour and then *poof* empty again. Most solid foods stay in the stomach for around an hour as they break down into something the body can process. nutrients are absorbed primarily in the intestines, not the stomach. Any nutrients absorbed would vanish at the appointed time, potentially seriously disrupting the cellular processes.