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BMI Increasing as Weight Decreasing?

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Hi there! I finally hit my 20 lbs lost mark today, but was very surprised to see my Aria 2 report my BMI was the highest it’s ever been since I started using the Aria 2. In fact it’s a significant jump from my last BMI. Any ideas why?

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Matt | United States | Texas
Alta HR & Ionic, Aria 2
Fitbit Coach & FitStar Yoga Premium
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A quick comment: you’re very likely confusing BMI (Body Mass Index) with body fat %. By design, BMI and weight always move in the same direction.

 

Now, your weight may go down, but your body fat % (as estimated by the scale) may go up, which feels counter-intuitive. This usually happens over short periods of time (a few days to a few weeks). Over a longer period of time, weight and body fat % should move in the same direction.

 

Also don’t forget that body fat % is an estimate. If you have lost 20 pounds so far, your actual BF% has most certainly come down too. You should be able to see this in how your clothes fit, for instance.

Dominique | Finland

Ionic, Aria, Flyer, TrendWeight | Windows 7, OS X 10.13.5 | Motorola Moto G6 (Android 9), iPad Air (iOS 12.4.4)

Take a look at the Fitbit help site for further assistance and information.

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4 REPLIES 4

A quick comment: you’re very likely confusing BMI (Body Mass Index) with body fat %. By design, BMI and weight always move in the same direction.

 

Now, your weight may go down, but your body fat % (as estimated by the scale) may go up, which feels counter-intuitive. This usually happens over short periods of time (a few days to a few weeks). Over a longer period of time, weight and body fat % should move in the same direction.

 

Also don’t forget that body fat % is an estimate. If you have lost 20 pounds so far, your actual BF% has most certainly come down too. You should be able to see this in how your clothes fit, for instance.

Dominique | Finland

Ionic, Aria, Flyer, TrendWeight | Windows 7, OS X 10.13.5 | Motorola Moto G6 (Android 9), iPad Air (iOS 12.4.4)

Take a look at the Fitbit help site for further assistance and information.

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Thanks for the information! You are correct, I was confusing BMI with % fat. I’m still put off that my % fat seems as variable as it is, but I suppose one month of data may be insufficient to really establish the overall pattern. 

Matt | United States | Texas
Alta HR & Ionic, Aria 2
Fitbit Coach & FitStar Yoga Premium
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There are so many factors that effect the Body Fat% estimate provided by impedance type measurements such as Aria scales and hence they can be notoriously inconsistent.  Hydration is one of the factors.  You can't really take any one measurement as accurate but rather keep an eye on trends over months.

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The only way for BMI to go up when weight goes down is to get shorter.

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