system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Why does the body burn muscle before fat when starving?

This is something that just doesn't make sense to me. I've read many times that when food isnt available the body will burn muscle before burning fat. Why? Why would the body burn what you need to move and get food to make sure you dont starve over what reserves it has incase food isnt available?
gpt
Our bodies don't default towards having massive muscles. Big muscles means you need more food to fuel the body. So if our bodies aren't getting enough food, our bodies go "We've got to shrink down because we're in a famine. Burn some of that fat for energy, and also some of the muscle mass as well, so we reduce the amount of muscles we need to feed. We're in a famine, and need to get smaller so we use less food and thus are more likely to survive."