Right, but that's just regular metabolism. In the context of this thread, parent poster claimed it wasn't all that's happening and it certainly won't account for 0.5 lbs of mass lost during the night (mentioned elsewhere in this thread).
It seems I have to be careful about my statements. I lost .5 lbs of mass (on average it was over this like .57 lbs) every day for 30 days. Some days I lost more some less.
What I found was that during the day I gained weight consistently from morning till night. I drank water, ran (2 miles then later 3 miles around 4:30pm) ate food (one meal at around 5:30pm), sweated on my runs, bowel movements were every couple days, urinated multiple times a day.
But, consistently gained weight morning -> night. I measured my weight Morning > noon > evening (before meal) > night (before sleep). Only in the morning after urination did weight leave my body. Otherwise is consistent gains.
People want to claim "it's all water", but that is nonsense, as I lost 15+ lbs that month.
So, during a few days, I stayed up all night, no extra water in the night, no urination until morning to see if it was just that 8 hour period (approx) that caused the final loss of total weight to get me to my lowest measurement of the day.
Nope. I had not lost any (or negligible weight, I was still at or near night weight). After I slept, (I'd wake in the afternoon) urinate, and I was back to my expected morning weight - with the average loss of .5 lbs.
Sleep has an effect on the processing of urine related to the expulsion of waste and the metabolism of fat. That is my theory. A lot of people here are calling this asinine, so be it.
If you are up for experimenting, weigh yourself in the morning and night for a week. Then stay up all night and weigh yourself in the morning, then after you get a nap. Then tell me I am crazy and there's nothing to this effect.