system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: What is happening in my body when I get the feeling I'm hungry?

Basically when I get hungry, I'll get this almost sick feeling. I can feel air bubbles or something moving around and coming up and it's uncomfortable. What is going on?
gpt
A lot of the sensation of being hungry comes from your brain and not your stomach. You often feel hungry in response to changes in your blood sugar level rather than the fullness or emptyness of your stomach or intestines.

When you actually do feel pain or discomfort from your abdomen while being hungry, that means that part of your stomach or intestines are actually empty of food and bile, but the involuntary muscular contractions that help you digest food are still taking place. A 'bubble' may actually be a pocket of gas from digesting starchy food being moved back and forth by these contractions. It may also be air you swallowed. Most of the time it's just your stomach or intestines writhing, though.

Nice image, huh?