I often feel empty and want food post poop

That's actually a thing. It isn't super common, but there's a weird feedback that links between the gut and the brain..

Been over a decade since I read the paper on it, but it was something related to serotonin, colinerase, and another neurotransmitter I can't remember.

The pressure in the gut being relieved makes the brain release a batch of chemicals, even for people that don't experience the hunger surge. But for people that do, the combination and amounts are different, and set off hunger. Usually before the person is even finished, they'll have the first sensation of hunger.

Plus, some people interpret the feeling of an empty bowel that was previously putting a good bit of pressure on as hunger, even though they aren't the same.