Weird question

It's from water retention. At night you are retaining a bit of water from having eaten relatively recently. In the morning you haven't eaten recently, and your body isn't retaining as much fluid. You wouldn't see as much of a difference if you weighed after breakfast instead of before.

I see the same thing when I happen to weigh at night. Weighing that much really isn't needed, but I like seeing the water retention impact of what I've eaten that day, and it's given me a better sense of what my real weight probably is when I know I'm retaining fluid. So on days where I was in a rush and couldn't weigh until the evening and I see a number 2lb higher then my trend for the week, I know that 2lb will be gone the next morning and all I'm really seeing is that I'm still on track.

Part of it is due to water evaporation during the night. Part of it is due to urination. It is actually a little easier to pull water out of the blood while you're lying down.