Last night I weighed myself before bed. I did it five times over the course of an hour and the average of the five reading was 234.8 lbs.
I went to bed and slept for 7 1/2 hours.
This morning I got up and weighed myself before going to the bathroom. Again, five times over the course of an hour. The average of the five readings was 233.2 lbs.
So … where did the 1.6 lbs of weight go?
Did you breathe when you were sleeping? Did you keep the cells in your body alive? That takes energy. Also, did you sweat, or lose any moisture from the breathing?
There was once a guy who weighed people just before and just after they died, and claimed that after death they weighed a bit less, attributing that difference in weight to the departed soul. Are you feeling particularly soulless today?
Hey! Wait a minute! I was 1.6 pounds heavier this morning. Please pick up your missing weight as soon as possible.
You know, I’m beginning to think that there are an infinite number of Straight Dope columns and forum threads, because just about every topic I can google for comes up with a hint. I google for the amount of water lost on average by a human at rest, clicked on one of the first links, which happened to be in the Washington City Paper–and it was a Straight Dope column. According to the column, the “average healthy young male averages about 25 milliliters per hour, or 200 milliliters per eight hours of sleep.” Assuming that you aren’t too far off of that, you lost around 7 ounces of water that way, or around 0.43 pounds. So that leaves only 1.14 pounds for your departed soul.
You were excreting all night. It may surprise you to learn that the body’s primary excretory organ is not the kidneys, nor the colon, but the lungs.
You snored it out.
And a previous (2012) forum thread!
Once interesting, to me at least, aside in that one was the note that one loses more while asleep X time than quiet awake the same time.
The reason, apparently, is that one sweats more during slow wave sleep.
Still most of the loss is via respiration.
And Dreams. Each dream weighs at least 6 ounces. Don’t forget about the dreams!
Is that dry weight, or a wet dream?
Joe Piscopo used to imitate Andy Rooney. One of the things he would say as Rooney was, “Ya ever notice that when you’re born, everybody wants to know how much you weigh, but nobody wants to know when you die? You’re never gonna hear, ‘Rudy Vallee died today. He weighed 158 pounds.’” 
Perhaps the sweat glands too, at certain times of the year.
I engage in a recreational activity (which I’ve discussed elsewhere on this board) that entails being outdoors in the sun for much of the day. It this climate, at this time of year, that entails a LOT of sweating – we are constantly being reminded to stay hydrated! The club provides bottles of water which we go through like it was water.
But wait, there’s more! Back at home, I sweat like a broken-off fire hydrant all afternoon and evening, and it only barely slackens off all night.
That’s gotta be a lotta water. And water is heavy !
Bathroom/Home scales aren’t known for being all that accurate.
Did you have one of those dreams where someone is chasing you?
mmm
I have a home scale with a digital display; I don’t know how accurate it is, but when I first got it I was surprised how repeatable it is. If I weigh myself once, and then again five minutes later, it will be the same number.
I do question its resolution, though. The display reads to the 1/10 of a pound, but the number after the decimal is always even, so at best it’s 1/5 of a pound. But I think it’s much worse than that. Over time I noticed that certain numbers never came up. I’d weigh (for example) 207.6, or 206.2, but never anything in between. I don’t know exactly why it does that, but there’s definitely some rounding going on.
Interestingly this thread had a weight loss of 1.6 pounds, the last one had a weight loss of 1.5 pounds, and the study linked to in the last thread had 2 pounds.
That really is the range of loss over night. Mostly water (and that mostly respired out), and some carbon loss from sugars burned overnight. The SD column that claimed, without citation, only 200 ml (about 7 ounces) of water loss overnight is I think off.
The home scale is generally fairly reliable with itself, even if not accurate … IOW it may not reflect true weight, it may be off by a pound or so one direction or so, but it is generally consistently so over periods of time of a few days anyway.
Hmm. That’s weight exhaled, though. Hey OP, one of the very first things I do when I wake in the morning is get up to pee. This seems to be common. Did you weigh yourself before or after emptying your bladder?
No, “Cecil” explicitly claimed as both exhaled and perspired water loss. Did not include the carbon loss but that is a lesser amount.
The op also explicitly stated: “weighed myself before going to the bathroom”.
Now of course some of us don’t make it through the night without getting up and having some … water … and nitrogen and other … losses. But our op sleeps through and weighed several times before losing that not so wee little bit.
I loose about a pound of Angst in my sleep, but it is replaced by Despair when I wake up in the morning.
That wasn’t true for Karen Carpenter.