From NPR's Krulwich Wonders:

Here's a simple question: Why do you weigh more when you go to sleep than when you wake up? Because you do. In the video below, you'll see the evidence. You can check this yourself. Somehow, while doing absolutely nothing all night but sleep, you will wake up lighter.

This is not about bathroom stuff. If you awaken and weigh yourself even before going to the toilet, you will still be lighter than when you went to bed. Why?

The answer.

Thanks for that.. I knew it was breathing that did it but not how. There was some infomercial a few years ago that had this lady say you could lose weight just by learning to breathe a certain way. Humn... maybe she had a point.

I started to think that breathing made me gain weight in the morning. I would weigh myself first thing...& when I was losing weight I would be so happy with what I'd see that I'd then go back to weigh myself again (just to see the new lower weight again!) maybe 10mins, later before eating or drinking water or anything & I'd be disappointing by the weight being a few tenths more than when I first woke up. I checked my scale & moved it around & it would give consistent results... just different from when I first first woke up. I thought it must be my body had lower oxygen levels from sleeping & the more I would wake up & breathe deeper it must be filling my blood back up with oxygen.

Idk if any of that is true or what... but this story makes sense to me. My brain just can't think of how the reverse would work.

i thought the majority of weight loss came from breathing.. you exhale the calories in effect. I can wake up weight myself and go take a nap for 3 hours and be a pound lighter and enter that in my daily journal instead

I'm going back to bed.

Ok, I can go along with this, but why do you gain it back during the day? You are still breathing. Your house is still the same temp, with the same humidity level. Did I miss something? One time when I was super obsessive about weighing, I found out that if I weighed myself when I first got up and then again around 10 AM, I weight a bit less at 10 AM. And that was also the time when my weight would start to rise for the day.