RE: Re: tanita model

[Guest guest]

I suspect the Tanita may be flawed for much more than amusement and confirmation

of trends that are obvious to anyone with a mirror.

The impedance measurement approach if properly calibrated may give a fair read

of the composition of our legs and lower trunk, but

the greater part of our body is not directly involved in that leg to leg

impedance measurement.

I have pondered modifying my unit to connect one electrode to my hands and leave

the other connected to the feet pickup. This would

involve more of the body (and surely require a recalibration).

One thing that I've personally experienced which makes me very suspect of

accuracy is the rather severe volatility in readings

before and after urinating, BM, etc. I suspect changes to hydration level in the

lower trunk, changes local conduction and is the

source of the swings when the measurement of part of the body is extrapolated

out to a full body number.

This is clearly taking an electrical impedance measurement that " suggests " but

does not directly measure %BF. Involving more of the

body mass in the measurement, and refining the algorithm that converts this

electrical characteristic to a %BF could lead to a more

accurate approach. To wit, just adding something as simple as waist measurement

to the algorithm could be very helpful in predicting

body type. Perhaps combine a waist belt input apparatus with another electrode

for even more accurate full body impedance

measurements.

While this could provide far more accuracy it also would be not as easy to use,

and would require plenty of additional work

(research) to properly calibrate. I recall reading a paper about how the Tanita

was originally calibrated and I think they just

measured a bunch of college students to develop the tables/equations (this is

from my recollection so may not be accurate- like the

......).

While the Tanita accepts an age input I would be surprised if it was used for

much more than a fudge factor applying general trends

for older people. Since this is an indirect method, input of such data should be

done.

caveat: The above is purely my personal opinion and not based on much more than

speculation.

BTW, it's a fun blinky toy... and I use mine about 3x a week under as identical

conditions as I can manage. Doing that I still see

day to day readings from <8% to 11% or so. Surely if I didn't control for

conditions the swings would be much larger.

Note: I am a runner and typically make my measurements after my EOD runs. My

personal hydration level may in fact vary significantly

due to ambient temperature and water loss during run, salt supplementation, etc.

JR

-----Original Message-----

From: Rodney [mailto:perspect1111@...]

Sent: Tuesday, January 11, 2005 9:23 AM

Subject: [ ] Re: tanita model

Hi JR:

It seems as if you are saying that if one were to get a benchmark

measure of body fat via DEXA or immersion, then one could apply the

adjustment factor derived from comparing the DEXA with the Tanita

measurement to future measurements taken on the Tanita scale.

Is that in fact what you are suggesting? Or did I read into that

post more than was meant? It seems like that might be a great way to

do things.

Rodney.

--- In , " " <crjohnr@b...>

wrote:

" ................... it's a fine toy but the BF measurement is

only useful for relative measurements .............. "