App body fat calculation issue

[Patricksyj]

I am using Aria to measure body fat. In the android app, when I check the measurement list in "Weight", the weight is 75.9, and body fat is 22%. However if look at the graph of lean mass vs body fat, the lean mass is 60.8kg. With body weight 75.9kg, the body fat actually should be 1-60.8/75.9=19.9%. so there is 2% difference. Could anyone help to give a solution or explanation on this?

[Patricksyj]

However this issue has just happen recently. I checked the reading last week, the 2 figure actually match with each other.

[MarreFitbit]

Welcome to the Fitbit Community @Patricksyj , hope you're doing great! Body fat percentage often increases when one loses weight because of hydration levels. In the first week or so of eating better, most people tend to lose a lot of water weight, because their diet includes less salt and refined sugar. 

Body fat percentage is calculated as fat mass divided by total mass, so if you significantly lower the total mass while fat mass stays the same, the body fat percentage will increase. Even if fat mass is indeed decreasing, the total mass is decreasing more, resulting in an increase of body fat percentage.

If you continue to weigh yourself daily, you'll probably see that your body fat percent goes down on days when your weight fluctuates up since you're retaining more water those days. Similarly, on days when your weight fluctuates down, the body fat percent goes up because you're retaining less water.

There are two scale settings that will affect the way your body fat percentage is calculated.

The first setting is “regular” mode and applies to most people. This mode works well for people who don't get a great deal of exercise as well as those that exercise frequently.

“Lean” mode is intended for professional or very high-level athletes like marathon runners or body builders. Individuals with exceptionally low body fat relative to their muscle mass may want to consider lean mode; however, many very fit and active people still get more accurate readings in regular mode.

If the mode you've selected appears to be giving you an incorrect body fat percentage reading, you may want to switch modes. To edit the your scale's mode, sign into your dashboard and go to your Aria settings page. Look under the “People” tab, then select the appropriate mode. Once you weigh in and the Aria syncs, the mode will switch.

Hope this helps!