[dan1123]

The readings are also affected by how hydrated you are, which varies a lot throughout the day.

Funny thing, the scale also gives a % water measurement (which seems to be more stable than the fat % measurement). I don't know what could make the readings vary so wildly if it can measure water %, and has gender, height, and age data.

[USFRIENDINVICTORIA]

Interesting, I've never seen one with a % water scale — but, I haven't been in the market for one for a few years either. The b.f. estimate is derived from the difference in impedance between fat and lean body mass — so, it does seem strange that it the reports for % water are more stable than for % fat (obviously, the opposite of the actual case).