it's impossible gain or lose more than about .3 pounds of fat in a day, so there's no reason to flip out. Everything else a person loses or gains must be water or lean body mass (harder to put on or take off rapidly than fat!) A salty meal plus TOM plus a home scale could easily equal ten pounds gained in water/error.

If you exercise a lot, it's quite possible that 148 is a good weight for your height. Why not get your body fat tested and forget about the scale, aiming for 20% body fat instead?