My biggest weight fluctuation in a week was 97.1 Kg on Wednesday, eating a stupid amount of chinees food combined with a loud of fluids and waking up on Thursday weighing 100.4 Kg. So I decided to have a stupidly big ride and 3 poo’s. Weighing in at 97.5 on Friday.
So yea thing can change allot in a few days.
On a normal stable diet it usually is not tho. Try writhing it down for a few weeks and see what happens.
Also make sure the scale is on a flat surface and try not to move it around in the floor to much. That really messed with my weight data for weeks earlier this year.