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Thread: Body Fat page

  1. #1
    Diana Renata's Avatar
    Diana Renata is offline Senior Member
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    Primal Fuel


    When I joined my gym I got a free fitness analysis, and part of that included measuring body fat. They used that scale with the little hand grip, and according to that my body fat was 28%.


    I've been adding some muscle and losing fat, and I'd like to know what my percentage is now, but the scale isn't for general use and the office is closed when I go in for my workout. I'd like to figure it out myself if possible.


    What's your suggestion for the most accurate calculations?


  2. #2
    Anonymous's Avatar
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    you can buy the calipers and do it through that method. if you google, there's a few methods for measuring body fat using just a tape measure. One of them is the 'navy method'. I'm sure it's not the most accurate method out there, but it's one way to do it.


    i've been using my crappy scale and the guide in the 'protein power' book. for me. My scale puts me at 28% or so, the protein power guide puts me at 18% or so, and the Navy guide puts me at 15%. I don't know which one is the most accurate, I'm guessing the PP one is the closest, though, just by the look & feel of my body.


    I know that that doesn't particularly help you since I don't have any way to really compare them to what I actually am. The method as to how the inexpensive electronic scales work (like mine) is pretty flawed, so I'm guessing it's 10% high.


    Since we all carry body fat differently and are of varying ages, I'm sure that there's not a perfect method for everyone that's reasonably available. This wikipedia article goes through the various methods and points out some of the shortcomings of each:

    http://en.wikipedia.org/wiki/Body_fat_percentage


  3. #3
    Nick's Avatar
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    I find the electronic methods (Tanita scale, Omron handheld) to be variable and biased -- they tend to read low when you're obese, and high when you're shredded, with additional variability if your fat is distributed in a way they don't expect. Clinical application of the bioelectric method involves right hand to left foot, or vice versa, instead of two feet or two hands, for that reason.


    I like to use the US Navy scale and feel it gives me pretty accurate results (7-8 points higher than the handheld). Check out this page: http://www.ehow.com/how_4478873_calc...ercentage.html

    I just have the formula plugged in to the spreadsheet where I track my weight and waist measurements, so I get a calculation for it every day (MyoTape is the easiest way to measure body parts). Note: formula expects numbers in centimeters.


  4. #4
    Anonymous's Avatar
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    well, the electronic methods *are* flawed because of the technical nature of how they work. there's a certain amount of electricity that your body (and other things, as well) can hold, this concept is known as capacitance. The other concept is that there's a certain amount of resistance for electricity to flow through your body.


    the body fat readers generally use a simple capacitance test, I believe, to test your body fat. They put a small amount of electricity in your body to see how long it holds. Of course, this doesn't very easily take into account body moisture, or overall density as Nick mentioned. Or, for me, who has really dry skin, it's going to be biased anyways. I can't use my scale unless I'm fresh out of the shower. I still use it as an inconsistent consistency, though.


    The navy method is probably reasonably accurate. From what I read the complaint is that it can be gamed, but assuming not-gamed, it's probably somewhat near reality. I doubt some random person in the navy whenever came up with it, it was probably a consensus at the time as a reasonable manner to do it.


  5. #5
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    It's not quite that simple. I should note I'm an electrical engineer. Bioelectrical impedance analysis measures impedance, which is not resistance or capacitance, but a combination of resistance, capacitance, and inductance.

    Resistance only matters at DC (steady voltage/current), but impedance varies with frequency. A capacitor's impedance starts at infinity at DC (once it's charged, anyway, it doesn't conduct anymore), and goes to zero as frequency increases to infinity, and the opposite happens for an inductor. Thankfully, unless you are an android, there is probably not much inductive behavior in your body, except in nerve cells.

    BIA meters send a ~50kHz signal, and the resulting impedance measurement (and they should be able to measure phase as well, i.e. if the body were purely resistive, the current would be in phase with the voltage, or 0 degrees phase, and if the body were purely capacitative the phase would be offset by 90 degrees) lets them derive the resistive and capacitative components, which measures total body water, which together with weight lets it estimate lean mass and then by subtraction, body fat.


    Supposedly there are more advanced units that can do multiple attachment points and use a broader spectrum of frequencies to get slightly more accurate results, including looking at intracellular water, but that may be vaporware.


  6. #6
    xanderd's Avatar
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    I just got some calipers from Amazon quite cheap. According to them I am 10.2% fat, and using my electric monitor on the same day that reads 16.9%.


    My electric monitor does ask for various inputs such as age, gender, and even activity level, although I'm guessing the calipers are still more accurate


  7. #7
    Chunster495's Avatar
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    These accu measure calipers are pretty decent and cheap.

    I got mine from ebay for under $10 with the shipping.

    It's as easy to use and it's only one measurement and no complicated formulas to figure out. Just pinch, measure and read your reading on the chart. These are definitely more accurate than the electronic ones.


    http://www.accumeasurefitness.com/


  8. #8
    Jedi's Avatar
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    I have the ironman tanita which measures from both feet and hands, I find if I take a seven day average it is fairly accurate. I am at around 17.5% atthe moment.


    They key is finding one method you like and sticking to it as not are 100% accurate


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