As opposed to starting a new thread, this one seem on topic enough for my question (but if a mod feels otherwise, feel free to split the thread. )

What is a normal amount of weight to lose while sleeping?

I just started the Atkin's diet yesterday. The night before I started I went out and bought a set of scales. Just the cheepo $15 analogue bathroom scales (with the dial that turns when you step on the scale).

When I got home (about 9:30 pm) I weighed myself. The result was what I pretty much expected -- 170 lb.

I then weighed myself first thing in the morning (post-pee and post-shower, I think ) but I weighed 165 lb. Is this possible, or is my investment in cheepo scales the problem?

So, last night before going to bed (after jogging and showering) I weighed 168 lb. And this morning, I weighed 165 lb.

I'm guessing that weighing myself at night is not giving a true measure, but I'm not feeling too confident in the scales I bought either. Losing 3-5 lb in my sleep seems too extreme!

Any thoughts?