system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Why do I crave food that makes me feel like crap 15 after I'm done eating?
gpt
It depends on exactly what food you crave.  For a very long time, foods with high fat, salt, and sugar content were not the most common thing in the world and in many cases could make the difference between starvation and not.

On a different level it is possible that you crave them now due to a psychological dependence.  Maybe at some point your mind formed a connection between that food and a certain feeling.