system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Why do you often have less of an appetite when the weather is hot?
gpt
Some can be attributed to needing less input.  If your body does not need to create any warmth of its own because the weather is doing that for you, your body uses less than its normal amount.  Keeping warm is just one use of food energy, but a significant one.  Less drawn from reserves means less desire for food input.