Everyday Body Fat Level

[0ni]

I think it depends on the conditions it's tested under
Also if you're bloated or on diuretics it will skew the test somewhat, which is why your scales probably showed a higher percent at different times of the day and doing it through the feet is a silly way of testing anyway as you hold most of your fat on the abdomen lol

 

[KungFooGoo]

Gotchya, makes more sense.

 

[Darkoz]

Bioelectrical impedance analysis - Wikipedia, the free encyclopedia

Thanks for the link 0ni and also for your mature response which I assume was to supposedly prove some sort of point you were trying to make.

However, my original question was whether body fat can actually be measured as accurately to the decimal point, not the different ways body fat can be measured and nowhere does your posted link reveal this but rather it does tell me that BIA is just an estimate and not a very accurate one at that, which is commonly known anyway.

BIA[1] actually determines the electrical impedance, or opposition to the flow of an electric current through body tissues which can then be used to calculate an estimate of total body water (TBW). TBW can be used to estimate fat-free body mass and, by difference with body weight, body fat.

Nevertheless it is not a "gold standard" or reference method. Like all assessment tools,

Simple devices to estimate body fat, often using BIA, are available to consumers as body fat meters. These instruments are generally regarded as being less accurate than those used clinically or in nutritional and medical practice. They tend to under-read body fat percentage.[2]

 

[0ni]

You asked if it can be measured accurately
I said yes, why wouldn't it
You said why not
I gave an example of how 14 year old kids can measure it at least semi-accurately if done in the right way
The implications of this are that there will be methods of testing bodyfat that are a lot more accurate than a teenager can do (EG a DEXA scan)

I'm sorry this upsets you so much. I don't even get why you're arguing lol. You find it hard to believe that we have the technology to measure that accurately? Why?

 

[Darkoz]

You asked if it can be measured accurately
I said yes, why wouldn't it
You said why not
I gave an example of how 14 year old kids can measure it at least semi-accurately if done in the right way
The implications of this are that there will be methods of testing bodyfat that are a lot more accurate than a teenager can do (EG a DEXA scan)

I'm sorry this upsets you so much. I don't even get why you're arguing lol. You find it hard to believe that we have the technology to measure that accurately? Why?

You know what I'm just going to put you on my ignore list as it's obvious here and your other posts that you like to contradict and argue for the sake of it and you also lack any reading comprehension skills.

 

[oldcorollas]

Tanita say their BIA measurement calibration is based on DEXA results.
They say their BIA readings are usually within +/-0.4% of a DEXA results.

I got some of those scales recently (teh fancy ones) and throughout the day, fat % does change.... but the actual measured MASS of fat does not really change much (much less than 100g variation out of ~15kg for me).
ie, it changes with hydration levels (as does muscle mass) and i assume it will change based on electrolyte and all the other crap that affects it...

are they accurate to within 1% of a DEXA? who knows.. who realyl cares, as long as they are consistant


DEXA has been said to be accurate to within 0.4-0.7% (of body mass) for fat, and within 4.5-5.2% for lean tissue, with significant variation between machines. meaning.. the 5.6 is pretty meaningless...
The intra- and inter-instrument reliability of DXA ... [Obes Res. 2004] - PubMed - NCBI

what am i tryin to say? even DEXA is not "accurate" for measuring muscle mass, but both DEXA and BIA can be fairly accurate (0.4% DEXA and 0.4+0.4% for BIA) for measuring fat%...

the only really accurate way would be to cut someone up but would be a bit hard to put the bits back together...
short of that, DEXA is the best we have, even if it is not that accurate...

 

[oldcorollas]

easy to find studies showing good agreement between Tanita BIA and DEXA..
Obesity - Comparison of Three Bioelectrical Impedance Methods with DXA in Overweight and Obese Men[ast]
Comparison of body composition by bioelectrical impedance analysis and dual-energy X-ray absorptiometry in Hispanic diabetics


edit:
just for fun, weighed myself with Tanita BC621 innerscan 50V (the one with handles) this morning (weekly thing).
then drank 500mls water and immediately reweighed.
weight was exactly 500gram more (measures to 0.05kg), and all of that 500grams was attributed to fat (specifically in the body core, not limbs)..
that makes sense because total muscle weight wouldn't have changed, as water not yet absorbed. so it measured the muscle ok.

but it does show that BIA outputs are susceptible to errors, based on what's in your stomach, or how much water is being held in muscles.

 

[0ni]

You know what I'm just going to put you on my ignore list as it's obvious here and your other posts that you like to contradict and argue for the sake of it and you also lack any reading comprehension skills.

You started the argument by questioning what I was saying

 

[oldcorollas]

You started the argument by questioning what I was saying you dumb retard

Oni, i'm going to guess you are not a scientist?
measuring fat/muscle/bone in the body to 0.1% accuracy by any means is not possible.

 

[jzpowahz]

Well in the pictures and videos you post up you look like you're carved out of stone. No way would l have thought you were over 10% bodyfat.

Aaah. I suppose I was just keeping my expectations realistic (pessimistic?) so I didn't feel so bad if I ended up at 15% or something? But really, I had no idea. Would recommend dexa scan for sure for anyone who wants to know.

 

[PowerBuilder]

Interesting discussion. Let's continue but only with less name calling, more references and being open to the possibility of being wrong.

Darkoz, are you interested to know if 'i' can work out if 12.5% of your body weight is fat or 12.6%? If that's the case then let's look at a hypothetical example.

Jim has a TBW (total body weight) of 96.43kg according to the tool being used. 12.5% of that equals 12.05645kg of fat. 12.6 would result in 12.1527. That's about 9g.

If we wanted to be really clever we'd make several measurements then evaluate the mean average and accepting an epsilon/delta error margin of 0.56, which would make things even more accurate.

Think about the tool beig used and the maths being applied to he results. Te results are worthless if no realistic error margin is awarded.

Let's keep the broscience to the faux lifters,

 

[0ni]

Oni, i'm going to guess you are not a scientist?
measuring fat/muscle/bone in the body to 0.1% accuracy by any means is not possible.

I didn't say it was

 

[0ni]

If we wanted to be really clever we'd make several measurements then evaluate the mean average and accepting an epsilon/delta error margin of 0.56, which would make things even more accurate.

Yes this is exactly right, take a big enough sample size and the error margin is pretty much removed..

 

[oldcorollas]

Yes, why would technology be limited to only being able to measure to the nearest 1%

there are 2 main errors in any measurement.
the systematic error (how far from the real value it is), and the distribution of results (scatter).
by taking umpteen measurements, you can apply statistics to the scatter and work out the mean. that only takes into account the variability of the machine itself.

the systematic error is far harder to measure. you need a way to accurately determine the "truth" before associating a systematic error to anything.
If DEXA is the best we have (compared to BIA and water immersion), how do you calibrate a DEXA when the density of muscle, bone and fat varies for each person, and varies within each persons body?

you can calibrate it with "shadows", but if the subjects densities are different, the DEXA measurement will not be accurate. this could easily be a few BF% difference.

the real question is, how can any method measure body composition accurately at all? even when animals have been dissected and measured, the results vary greatly (for all body composition measurement methods).


in the end (like a chassis dyno for cars) as long as you use the same machine with the same calibration for all your tests, and mainly look at the change in measurement, rather than the absolute value, DEXA is the best you have.
if you use a different DEXA machine, or yours gets calibrated differently, the results are nowhere near as useful.

You asked if it can be measured accurately
I said yes, why wouldn't it because it cannot be measured accurately
You said why not
I gave an example of how 14 year old kids can measure it at least semi-accurately if done in the right way. "semi-accurately"? no such thing, and BIA is less accurate than DEXA, and based on DEXA results which are also innaccurate
The implications of this are that there will be methods of testing bodyfat that are a lot more accurate than a teenager can do (EG a DEXA scan) more accurate yes, accurate, no

I'm sorry this upsets you so much. I don't even get why you're arguing lol. You find it hard to believe that we have the technology to measure that accurately? Why?

why? because we don't. within +-2% sure, within +-1% very doubtful.

in the end does it matter? no

 

[PowerBuilder]

You asked if it can be measured accurately
I said yes, why wouldn't it?

What would you define as accurately

I gave an example of how 14 year old kids can measure it at least semi-accurately if done in the right way

Semi accurately? Is that like being 'sort of pregnant'? If I sai I lived within 2km of a certain beach, while that may be true....I actually live 1.8km away. That 2km vector is approximate just not impressively accurate.

 

[0ni]

I'm not going to argue semantics about what I define as "accurate"
Going to the point that was actually made about body fat being shown as "5.6%" it is perfectly possible for a result of 5.6% to be returned by a DEXA test

 

[oldcorollas]

oh sorry, i thought you meant that the 5.6% actually meant something
my bad
it could give you a result of 5.6435%, but still only "accurate" to within 2% or so

but you did ask why it couldn't be measured accurately.. and it can't..

 

[Morgan]

I'm not going to argue semantics...

That's all you ever do

 

[PowerBuilder]

I'm not going to argue semantics about what I define as "accurate"

It's not a hat question. It's not really an issue of semantics, it's just wanti clarification.

 

[0ni]

I think everything that can be discussed has already been discussed