system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Why are there typical breakfast foods and dinner foods? Is there a biological reason where we want certain nutrients at different points in the day or is it just a social construct?
gpt
Imagine you are are a preindustrial farmer.   You get up before dawn, toil in the field all day, then go back home when it gets dark.

For breakfast, you want something hot that will give you a lot of energy, but can be prepared quickly.

For lunch, you want a cold meal you can take with you and eat when you get hungry.

For dinner, you have time between sunset and bedtime, so you can take a little longer, and have something nice while socializing with friends and family.

The pattern of necessity has become ingrained in our culture, so we consider certain foods to be appropriate for certain meal, long after the original reasons were forgotten.