Comment by TeMPOraL

2 kilograms is about the upper bound of the expected daily weight variability of an adult, caused by water retention and food intake. It's the difference between what you see if you weigh yourself after taking a morning dump vs. after dinner. That's why people are advised to weigh themselves at the same time every day.

(For purposes of weight loss, normies are also advised to weigh themselves weekly instead of daily, because it's easier than explaining to them what a low-pass filer is.)