How come . . . .

[Evemariesaint]

I use scales which give you BMI, body water and fat percentage as well as weight, and I wondered why my body water percentage always goes up when my weight goes down and vice versa.
I would have thought the opposite would be true?

[Dominique]

You should pay attention to weight and fat over a long enough period of time (e.g. several weeks to several months). When doing so, you should see both moving in the same direction, if your scale has any level of reliability. Whatever changes take place in a short period of time (a few days to a couple of weeks) don’t really matter. It’s quite possible you see fat going up and weight going down (or vice-versa) over a one to two week period, although it doesn’t seem to make sense.