Body Composition Scales variability

HelenAnne · 29-04-2017 05:59PM #1

I have recently acquired a Body Composition scales (i think my parents got fed up trying to link it to their phones and just gave it to me and went back to a normal scales.)

Anyway, I know they're not super-accurate, but despite knowing that I am still frequently plunged into despair if it tells me my body fat has jumped up a per cent over night etc (I know it's affected by hydration etc, I'm just prone to believing the worst

) but I noticed that actually it has the weight of my BONES changing from day to day! Unless I'm having a very sudden attack of bone-density-loss, that can't be right!

So my two questions are: 1) if that's a bit odd does it mean all the measurements are probably wrong and 2) if hydration can make body fat levels appear to go down on the scales, what change might be making bone weight seem to go up and down?

glacial_pace71 · 29-04-2017 07:16PM

At the outset I'll confess that I've no knowledge on the BIA element, but you've described the known issues anyway in terms of hydration etc:

https://en.wikipedia.org/wiki/Bioelectrical_impedance_analysis

My knowledge, (dated though it now is), on the issue of bone density, is that there are huge variations. I once worked in the immigration area. As you'd imagine it'd be a major child protection issue if a fully grown man (with a lot of facial hair, a deep voice etc) sought to be recognised as an unaccompanied minor and so be housed with children.

The bone mineral density (BMD) tests (which is essentially for calcium density) would provide age ranges are subject to huge variations in the 't scores' and 'z scores', depending upon whether there's been any trauma. As an athlete you'd undoubtedly have had issues with everything from metatarsals to 'shin splints'. One of the biggest problems is the use of the tibia as a reference bone, together with oesteons. Being athletic, your age could well read as being that of an osteporithic old lady or of a 15 year old girl.

Bearing that in mind, I'd treat the accuracy of BIA on a similar scale of the BMD tests. However, with BMD you can get radiation-related complications from overuse, but with your BIA scales the only risk (however remote) would be of electrocution.

I wouldn't use a BIA scale but I'd imagine it'd be useful for athletes: every few years in my workplace we get a free health check-up. Inevitably a squeaky-voiced trainee/newly-qualified doctor looks at the scales, his/her charts and declares that I'm overweight or obese. (I don't deny the former over the latter but the lazy use of BMI is annoying when the subject of the supposed medical examination is muscular. Ok, flabby and muscular, but it'd still be a speed and strength warranting at least a cursory glance at an alternative set of calculations of muscle:body-fat ratios).

Sorry, short answer: have a BMD test, then you can say 'you lie!' to the BIA scales every time the reading gives an outlier as a reading.

HelenAnne · 29-04-2017 08:52PM

Thanks, that's all really interesting about bone mineral density etc!

I was really just wondering (out of interest, on a whim) what kind of day to day thing might skew Bone Weight readings (the way water etc skews fat readings) -- I'm not actually worried about my own bones, I'm just presuming the stupid scales lies if it tells me they've got a good bit heavier or lighter since yesterday

I planned on not giving much credence to the scales, when I acquired it, but it's weirdly compelling to get a little graph on your phone whenever I weigh in :eek:

thanks again!

ETA: I wouldn't call myself an athlete, btw; let's say 'enthusiastic recreational runner'

Body Composition Scales variability

Comments