system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5 Why do you not feel hungry when you're sick?
gpt
There are advantages to eating less.  Digesting food requires energy.  That energy is better used by your immune system.  Eating less can result in lower iron in your blood, which can sometime starve the bacteria that may be causing you to be sick.

Those are the reasons why it can be helpful to eat less.  When we are sick our bodies release cytokines, which among other things, reduce our apetite.