system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: How does sleep deprivation lead to other bodily issues such as an upset stomach?

I’ve read that not getting enough sleep can cause a myriad of issues such as upset stomachs or pain at times.  How does missing a bit of sleep cause such seemingly far flung bodily issues?
gpt
Your body is supposed to work like a fine-tuned machine.

However, even fine-tuned machines get out of tune when put under too much stress.  Sleep deprivation causes your body to change how it distributes things that help your body function.

Three main things (hormones) your body alters are cortisol, ghrelin, and leptin levels.

Ghrelin tells you when you're supposed to be hungry.  

Leptin tells you when you're full.

Cortisol fixes sugar levels in your blood, and is created when your body is under stress.

These three things combined change not only your hunger levels when you're sleep deprived, but they can also change what foods you're hungry for.  They can change how your body stores fat, they know what times of day you normally eat.

Sleep deprivation throws all of these things out of balance, and those things are tied to your digestive system, your immune system, and more.  Extended sleep deprivation is tied to diseases like diabetes and heart disease.

In short, get some sleep!