Lose almost 10 % body fat in under 3 hours! (Why scales are bullshit)

_{By scottwebb on pixabay.com}

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"Suesa, how has the fact that you're studying a field of science influenced your life?"

"Not much", I tend to answer. But today, that was proven wrong.

For months, my fitbit scale Aria 2 has shown me what I perceived as wildly inaccurate body fat measurements, which had increased over time. Now, while I didn't really give a fuck about the number (which ranked me as more and more obese), I was a bit peeved about the consistent upwards trend because

• I'm doing strength training 5 times a week
• The weights I've been lifting have been increasing
• I track the amount of protein and calories I eat
• I know I don't look obese

These things were enough for me to try and find a solution. When you check the Fitbit FAQ about this scale, you find this:

_{help.fitbit.com}

Wikipedia (yes, I am lazy today, there's a reason this is not on my official account) says the following about bioelectrical impedance analysis:

Bioelectrical impedance analysis (BIA) is a commonly used method for estimating body composition, and in particular body fat. Since the advent of the first commercially available devices in the mid-1980s the method has become popular owing to its ease of use, portability of the equipment. It is familiar in the consumer market as a simple instrument for estimating body fat. BIA actually determines the electrical impedance, or opposition to the flow of an electric current through body tissues which can then be used to estimate total body water (TBW), which can be used to estimate fat-free body mass and, by difference with body weight, body fat. Source

Hm, so we actually determine total body water? Well, I'm always doing the measurement right when I wake up, but the amount of water in my body might still fluctuate a bit ... could that be the reason?

But when I google "Aria 2 body fat inaccuracy" I get several hits. More people seem to have this problem, and two main suggestions to fix it stood out:

• Check that you have entered the correct sex (apparently male and female calculations differ)
• Remove the batteries from the scale and put them back in (Have you tried turning it off and on again?), then re-calibrate by weighing yourself three times.

Fitbit had registered me as female everywhere, so I did the battery thing and got on the scale.

And my body fat percentage dropped. Each time.

I checked the app again and found the so-called "lean mode".

_{help.fitbit.com}

"Why not", I thought. "I am building muscle after all."

The percentage dropped again. I kept getting on and off the scale, to see when it would stop dropping.

But it didn't.

While my weight (which I blacked out here, because for some reason I feel uncomfortable showing it) kept relatively stable (in a 100 g range), my body fat percentage dropped from 28.3 % to 19.1 % (actually 19 % but I forgot to take a new screenshot), in a span of 2 hours and 20 minutes. You can see that between measurements, there's about a 1-2 minutes delay, as the scale had to synchronize with the database each time, before I could measure myself again.

After hitting 19 %, I gave up. I had just wasted a huge amount of time and felt severely dehydrated.

So, to return to the question from the beginning: How has my field of study influenced my life? Well, apparently it has created the need to do stupid experiments for hours.

I'm still not entirely sure what the problem is, maybe a rounding error as @lemony-cricket suggested (thanks for chatting with me through all of this, I would have been so bored otherwise), maybe something else. Maybe lemony's other idea, that "It zaps fat from your body, it exchanges one fat for three cancer" is the truth. Who knows?

In the end, I'll probably turn off the body fat measuring feature now, as it has proven more useless than I already thought it is. And if you have been looking for a convenient way to measure your body fat at home, this is not it.