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electic body fat percentages

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01 / Original postelectic body fat percentagesRobert Grumbine · 30 Sep 2004 02 / This pagePosts 1–10Page 1 of 1 · chronological order 03 / Latest replyPost #10Barf Bag · 1 Oct 2004

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General fitness, health and nutrition
Published
30 September 2004
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1 October 2004
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Robert Grumbine
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  1. Original post
    Robert Grumbine
    Archived post
    #1

    We have one of the electric (hand held) body fat meters at work
    and, having discovered this, I've taken a couple of measurements.
    After Tuesday's had it that although I'd lost 6 lbs (welcome) in
    the last 2 months, I'd gained 4 lbs of fat (not bloody likely!),
    I did a rerun today, where it said I'd retained all my fat, but
    had lost 8 lbs of lean mass (also not likely).

    I then fooled around a little with it, and found that changing
    from normal to athletic dropped the reported % by 3.3. Given their
    standard for athletic, I could be near 'highly athletic', which
    would, perhaps drop the reading further. Changing my height from
    6'0" to 6'1" reduced the reading by 1.1%. I do have long arms
    (and legs) for my height, so, again, a question about what it's
    really measuring and how best to get it to represent what's really
    going on in my body.

    Or just something to ignore. What are the standard error,
    bias, etc. figures for such systems?

    Since the reading changed markedly (6.4%) for holding the meter
    with my arms bent, rather than fully extended, I'm guessing that
    it's not measuring resistence. Probably capacitance instead.
    Anyone know for sure?

    --
    Robert Grumbine http://www.radix.net/~bobg/ Science faqs and amateur activities notes and links.
    Sagredo (Galileo Galilei) "You present these recondite matters with too much
    evidence and ease; this great facility makes them less appreciated than they
    would be had they been presented in a more abstruse manner." Two New Sciences

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  2. Barf Bag
    Archived post
    #2
    Quoted message said:

    We have one of the electric (hand held) body fat meters at work

    Why? You need a machine to tell you you're fat? I can look at your fat ass and
    tell you you're a fat pig. No fancy machine needed.

    Report
  3. Bear G
    Archived post
    #3
    Robert Grumbine said:

    We have one of the electric (hand held) body fat meters at work
    and, having discovered this, I've taken a couple of measurements.

    I think those are considered pretty much useless. The ones built
    into scales are better, and even better are the leg-to-arm ones
    you'll find at expos.

    Quoted message said:

    Or just something to ignore. What are the standard error,
    bias, etc. figures for such systems?

    I have one of the scales although it hasn't worked in over a year.
    The instructions warn that readings will vary by several points
    during the course of the day. They're really designed for
    long-term monitoring under identical conditions so you can track
    changes.

    What I would do is take readings on Friday, Saturday and Sunday
    shortly after I got up, then use the median value.

    Quoted message said:

    Since the reading changed markedly (6.4%) for holding the meter
    with my arms bent, rather than fully extended, I'm guessing that
    it's not measuring resistence. Probably capacitance instead.
    Anyone know for sure?

    I believe they use impedence.

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  4. np426z
    Archived post
    #4

    "Robert Grumbine" <[email hidden]> wrote in message
    news:[email hidden]...

    Quoted message said:

    Since the reading changed markedly (6.4%) for holding the meter
    with my arms bent, rather than fully extended, I'm guessing that
    it's not measuring resistence. Probably capacitance instead.
    Anyone know for sure?

    OMG! You also calculate the standard deviation for the number or
    cornflakes in your breakfast cereal packets each year, don't you?

    Report
  5. Donovan Rebbechi
    Archived post
    #5
    np426z said:

    "Robert Grumbine" <[email hidden]> wrote in message
    news:[email hidden]...

    Quoted message said:

    Since the reading changed markedly (6.4%) for holding the meter
    with my arms bent, rather than fully extended, I'm guessing that
    it's not measuring resistence. Probably capacitance instead.
    Anyone know for sure?

    OMG! You also calculate the standard deviation for the number or
    cornflakes in your breakfast cereal packets each year, don't you?

    What a great idea!

    You could weigh your servings, then estimate the sampling distribution
    by weighing a few manually hand-counted samples of 50 or so. That way,
    you could not only graph your daily cornflakes intake in the training
    spreadsheet, you could also put error bars around the plot. No doubt this
    would result in a dramatic improvement in performance (provided that
    the estimates were accurate to 5 significant digits, of course).

    Cheers,
    --
    Donovan Rebbechi
    http://pegasus.rutgers.edu/~elflord/

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  6. Surf McBrowse
    Archived post
    #6

    Hope you like your cornflakes dry. You'll have to bake all the moisture out
    of them so as to determine the dry weight (otherwise your bowl to bowl
    results will be skewed by variations in humidity). Unless of course you're
    prepared to open, store, weigh and consume them inside a humidor with an air
    lock.

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  7. Donovan Rebbechi
    Archived post
    #7
    Surf McBrowse said:

    Hope you like your cornflakes dry. You'll have to bake all the moisture out
    of them so as to determine the dry weight (otherwise your bowl to bowl
    results will be skewed by variations in humidity). Unless of course you're
    prepared to open, store, weigh and consume them inside a humidor with an air
    lock.

    Good point -- but you could measure some first under various room conditions,
    then compare the room weight to the dry weight, that way you could estimate
    the effect of the humidity on the mean density of each cornflake.

    Cheers,
    --
    Donovan Rebbechi
    http://pegasus.rutgers.edu/~elflord/

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  8. Phil M.
    Archived post
    #8

    Leafing through rec.running, I read Robert Grumbine's message of 30 Sep
    2004:

    Quoted message said:

    We have one of the electric (hand held) body fat meters at work
    and, having discovered this, I've taken a couple of measurements.

    The more hydrated you are the lower the body fat reading.

    Phil M.

    --
    "Learn from the mistakes of others. You can't live long enough to make
    them all yourself." ­Martin Vanbee

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  9. Surf McBrowse
    Archived post
    #9
    Quoted message said:

    Good point -- but you could measure some first under various room


    conditions,

    Quoted message said:

    then compare the room weight to the dry weight, that way you could


    estimate

    Quoted message said:

    the effect of the humidity on the mean density of each cornflake.

    Hmm, sounds tedious, I like it. If you can write the equations to estimate
    the dry weight of a corn flake given the ambient temperature, relative
    humidity, barometric pressure, elevation, gravity (may vary) and phase of
    the moon; I'll write the computer program to accept the variants and spit
    out the answer (with lots of nifty configurable menus and some slick
    graphics to boot). We could then couple it will a database training log and
    export the data to Excel. "The Runners Cornflake Diet and Training Log".
    We'll be rich!

    Report
  10. Barf Bag
    Archived post
    #10
    Quoted message said:

    We'll be rich!

    I'd change my name to Rich too, after that post.

    Report

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