Out of curiosity, I weighed before bed last night and was 159.0. This morning I was 157.6, which I round up to 158 for reporting. I plan to go to the gym early AM tomorrow.

When digital scales are out of whack, the cause is usually mechanical as odd as that sounds. The ICs that turn the pressure on them into a number are highly accurate with a low failure rate. The difficulty is getting all the pressure on them and not allowing weight to transfer around them. That's why carpet can be a problem. Holding on to something, even as lightly as you can will throw them off. Unfortunately, so can swaying, so if you can't stand straight and still unsupported for a few seconds, it is hard to get an accurate weight. Weight distribute evenly between feet and between heel and ball of each foot helps.