Incorrect body fat %?

bobbyjodearnley

So I measured myself today on one of the body fat scales in boots
My stats were
5ft4.6
121lb
Bmi 20.4
Body fat 17.1%
It all seems reasonable except my BF%. I have a small frame and a lot of pinchable fat so I would expect it to be over 20. (Apparently I was 18.5% 3 weeks ago on the same machine)
I know that these machines can be a bit off but do you think it's mainly the machine or could it also be I carry most of my fat subcutaneously and have less than average around my organs etc? Could that account for some of the difference? I look nothing like the pictures of other women with 17-18% bf I've seen on the internet!

Only 11lb left to go though

asciiqwerty

the machines are estimating BF often given weight and height data
the equations they use may or many not account for many things, including gender

there are lots of different equations you can use, some of them are available on line that work with height, weight and a few measurements, they are all estimations, and if you use three you'll get three different results, but it you use three persistently over a period of time, you'll see that they all show the same trends

ps. great work on getting to 20 bmi

SnuggleSmacks

Actually, most of these machines measure bodyfat by bioimpedence...which means it sends a small electrical current through your body and measures how it's conducted. Lots and lots of things can throw it off, because it can only distinguish between fat/not fat, so if you're wearing different clothes, have a different level of hydration, or ate more or less since your last poop, then it's going to change the percentage of fat.

These scales work best if you always measure at the same time of day, when you first get up, before eating, naked, and preferable after a poop. Either never drink a glass of water first, or always drink a glass of water first. Keep as many factors as possible consistent.

edited to correct typo

asciiqwerty

true for most of the scales people have at home

for the ones in shops like in the boots near me or pharmacies where you don't hold anything or take off your shoes and socks they can't be using bioimpedence

though even bioimpedence machines use empirical equations to turn the resistance to the current (which they measure) into a BF value

and still the trend, on a given machine over time, is more important than the value

bobbyjodearnley

you have to hold the handles on this one so I think it does :P

bobbyjodearnley

aint going into a public shop naked, sorry :')

asciiqwerty

for comparisson you could put your data into one of the many estimators available online that use measurements, what you'll see is that they will all give you different results (they are based on empirical equations) but if you track them say weekly over a month or so their trends will look similar even though the values are different [at least they are for me, I would tend to ignore one if it gave a different trend]

No_Finish_Line

no matter what test you use there is a good chance your not really getting an accurate BF%

so even tho the online ones where you enter your measurements are the least accurate, they would be the most useful to measure progress, because you know that the difference in out come is based on the differences in tape measure measurements. where as with the scale how much water you are carring and a number of other things that have nothing to do with bodyfat and are more or less out of your control will effect the outcome.

No_Finish_Line

and i'd assume that wearing shoes would make a difference for the ones that use an electrical current.

wilsoje74

I would not trust those machines at all