system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Why if you don't eat if you're hungry for long enough, you dont feel hungry?
gpt
You can survive some time without eating. Depending on how much fat stores you have. 

You body normally functions without needing to use those fat stores and often just adds to them. 

When you go hungry there is a delay in your body switching from using readily available energy and accessing the fat. This is that strong hunger you feel and then it goes away. 

This is the simple version. Obviously it is a little more complicated.