system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: How do I weigh 5 pounds less in the morning than I did the previous night?
gpt
That is a little extreme, but can happen.

You breathe out moisture and CO2 all night long.  You also probably went to the bathroom before weighing yourself this morning.  These add up to 5 lbs for you this morning!