system
Given the following post, respond as if you're commenting on Reddit:
human
Why does your appetite slow down when you’re sick?
gpt
Firing up the immune system releases hormones that suppress appetite.

One theory is that if you don't eat, the blood sugar goes down, starving bacteria.  

The theory behind intermittent fasting is that the body's cleanup system is triggered by fasting.  That would be particularly useful to clean up the detritus of the immune system attack.