My weight is so stable that I ran some test. One in nude as my referance, another with a small box of books. Then one with a couple of heilum balloons.
TEST standard was 230 LB, The standard with books 238 LB, and the standard with the baloons was 230 LB (A girl can hope). I did this to make sure the scales were working correctly.
What is interesting is if Dry (before a shower) I am 230 LB and dripping wet (fresh out of a hot shower) I'm 228 LB. Turns out the heat and humidity is playing with the elasticity of the spring in the scales.