Is it possible to put body fat on ‘overnight’ without putting weight on?

[TraceSPN]

A bit confused.

Yesterday my Aria scales read 77kg and 41.2% body fat. 

This morning, they read 77kg and 41.8% body fat.

Only difference in my days was that I did a HIIT class first thing.   Had a calorie deficit of 1000 calories. Always weigh myself at the same time every morning. 

How can this happen? 

[Heybales · Accepted solution]

It happens because a BF% scale can not possibly be that accurate.

5 - 10% if you happen to present the exactly same hydrated body to it.

Even the scale part of it - I wouldn't be surprised if the specs say that while it may read to 0.2 lbs for display, the accuracy is only 0.5 lbs.

The difference between BF and LBM (Lean Body Mass - everything not fat) is calculated using statistics, gender, weight, maybe height and age, and sending impulses of current through your body. In this case up 1 leg and down the other, and reading the resistance (BIA scale).

You drink 16 ozs of water and your LBM will go up and BF will go down. Even though nothing changed in reality.

In this case, both measurements fall within the at best (and not likely) 5% accuracy range.

There was no change in reality.

Track the BF% over the course of months to discern a direction - that's what it's good for.

Well, if it's consistently off anyway, I haven't seen any testing of it like other scales to know if that's the case.

[TraceSPN]

Thank you!

I’ve been wondering about the scale accuracy as well.  If I use the standard medical grade scales I bought to weigh my Mum on, they are always half a kilo lighter than the Aria weight.