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  1. #1
    So say we all.
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    Accuracy: body fat scales?

    Heya -- anybody know how accurate the bodyfat measurements of these new-fangled digital scales are? I'm thinking maybe it's my calloused farm-boy feet that make it think I'm a lard-o, and not the donuts.

    I googled but all I get are ads for scales and ads disguised as product reviews (thank you, Women's Health.)

  2. #2
    Permanent Amateur Mark B10Cycle's Avatar
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    They're very inaccurate, at least in my experience. I bought one a couple years ago, which wasn't cheap, and used it for a while. I then had to have my body fat tested for wrestling, so I had it tested by a doctor with the calipers and pinching. I was told I had 7.5% body fat. I immediately went home and hopped on my digital scale to cheeck the body fat and see how accurate it was. It read 14% which I then knew was untrue.

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    bac
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    They are not necessarily accurate in terms of an absolute body fat percentage, but they are still useful. These scales are useful in showing your long-term change in body fat - the trick is to weigh yourself @ the same time of the day.

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    My experience has been the same as B10Cycle's. My scale always has me between 13.5-15% while calipers, which are supposed to be a more accurate measurement, have me between 7-10%. The scale also seems less likely to show a drop during times when I'm training hard and I know that my fat % should be decreasing.

  5. #5
    Senior Member rich007's Avatar
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    You should guys try Tanita models with 'Athlete' modes... Those body fat measurements should be closer to real BF%, when you exercise more than 10 hours weekly... At least, that's what's advertised... (Don't have personal experience with them, but I'm looking into buying one like that... Anyone wants to add pro/con comments about them??? Thanks...)

    Then again, all of the BF% scales compute the BF% on some kind of statistical average... Also, you'll get different measurements depending on how humid it is, body hydration levels, times of day, etc... The best thing to do is to do it at the same time of the day for the whole week and average the results... Just my 2 cents...

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    Permanent Amateur Mark B10Cycle's Avatar
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    Quote Originally Posted by rich007
    You should guys try Tanita models with 'Athlete' modes... Those body fat measurements should be closer to real BF%, when you exercise more than 10 hours weekly... At least, that's what's advertised... (Don't have personal experience with them, but I'm looking into buying one like that... Anyone wants to add pro/con comments about them??? Thanks...)

    Then again, all of the BF% scales compute the BF% on some kind of statistical average... Also, you'll get different measurements depending on how humid it is, body hydration levels, times of day, etc... The best thing to do is to do it at the same time of the day for the whole week and average the results... Just my 2 cents...
    That's what I have. Not too accurate, but the others who posted made a good point: use it to compare your changes based on whatever it reads.

  7. #7
    Senior Member rich007's Avatar
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    Quote Originally Posted by B10Cycle
    That's what I have. Not too accurate, but the others who posted made a good point: use it to compare your changes based on whatever it reads.
    Thanks, good to know...

    I thought they might have been more accurate than the regular models... I had a regular TANITA model until it broke... (w/o the 'Athlete' mode and it showed 15-17% fat while I was more like 10-12%...) Now, I just use a regular body weight scale... Guess, the TANITA models are not worth that much then...

  8. #8
    SSP
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    I have a Tanita with the "regular" and "athlete" modes, but find that the "regular" mode overstates my body fat, while the "athlete" mode understates it. However, if you take your measurements carefully (particularly with regards to your hydration levels), it is consistent over time, even if it's not "accurate".

    FWIW, you might want to try the "Navy" body fat measurement approach. It requires taking a couple of body circumference measurements, and seems reasonably accurate, assuming you are careful in measuring. I've reviewed their research that went into the development of their formulas, and it seems like they put some significant thought (and taxpayer dollars) into it. Probably less accurate than the "dunk tank", but just as accurate as calipers.

    I've built the Navy method into my CycliStats and WeightWare programs, or you can find it online at http://www.he.net/%7Ezone/prothd2.html .
    CycliStats.com - Software for Cyclists
    WeightWare.com - Weight Management Software

  9. #9
    Senior Member rich007's Avatar
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    Quote Originally Posted by SSP
    I've built the Navy method into my CycliStats and WeightWare programs, or you can find it online at http://www.he.net/%7Ezone/prothd2.html .
    That's more like it... :

    Your Recommended Blocks
    Your weight is: 167 pounds
    Your sex is: Male
    Your Body Fat percentage is: 10
    Your Lean Body Mass is: 150 pounds
    Your 'Ideal' weight is: 173 pounds
    Your activity factor is: 0.87

    Thanks...

  10. #10
    Videre non videri
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    There are two things to this - accuracy and precision.
    Body fat scales aren't particularly accurate, but they generally have good precision.
    That is, they're not good for absolute body fat measurements (poor accuracy) but they're consistent for the same person, under identical conditions (good precision).

    If you're overweight and you use the BF-meter to help you make sure you're losing fat, not muscle, you can rely on it.

    Let's say you start out at 200 lbs and BF at 40%. Your fat weight is then 80 lbs.
    After four months, you've lost 25 lbs. Your BF reading is 32%.
    If you've lost 25 lbs of fat, that means you've got 55 lbs left, and your new weight is 175 lbs. 55/175=0.314, or 31.4%. So you've lost fat and almost nothing else.
    (That's not realistic though - you'll always lose a little muscle no matter how good your diet is!)
    If, on the other hand, your weight was down to 175 lbs, and your BF showed as 40%, that means you've only lost 10 lbs of fat, and 15 lbs of muscle mass!
    Not good...

  11. #11
    The Question Man
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    Well I recommend staying away from any Taylor scale. I weighed myself last night and to my surprise I was at 168.8. This got me curious as to why I had a weight gain over the period of one week of 3+ pounds when I'm on a 1800-1900 calorie diet coupled with 3-4 hours of exercise each week (not counting going to class everday which is waking up at 8 and walking a few miles to and from). So this morning I decided to weigh myself again and poof. I had dropped 4.6 pounds overnight! Taylor = Sucks I mean I understand that weighing in at night and in the morning will give you different weights but 4.6 pounds different? That's quite a big difference.

    Edit: This taylor scale is a body fat analyzer as well but I'm beginning to doubt its accuracy.

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    Senior Member late's Avatar
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    The problem with those damn scales is that you would need to chart
    your bodyfat over a period of months to miminise the measurement error. That error is massive. If you want a device to actually do it's job, the Tanita is a waste of money. A change of temperature will change the humidity on your skin (sweat) which, in turn, will make for a large change in what it says your bodyfat is. Having gone through all this, my conclusion was that outside of a lab you aren't going to get an accurate measurement. You can weigh yourself with great accuracy, and use that to keep track of how things are going.

  13. #13
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    Actually, I have a Tanita model, and it was perfectly consistent for me.
    The variance was no more than 1% at any time.
    I started out with an indicated 28% and am now at 18%.
    My estimate is that my actual BF% is around 22-25, but that's not the issue.

  14. #14
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    I found a good webpage which talks about the accuracy of various body fat measurement techniques, which includes references.

  15. #15
    Senior Member peterm5365's Avatar
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    Quote Originally Posted by cheebahmunkey
    Well I recommend staying away from any Taylor scale. I weighed myself last night and to my surprise I was at 168.8. This got me curious as to why I had a weight gain over the period of one week of 3+ pounds when I'm on a 1800-1900 calorie diet coupled with 3-4 hours of exercise each week (not counting going to class everday which is waking up at 8 and walking a few miles to and from). So this morning I decided to weigh myself again and poof. I had dropped 4.6 pounds overnight! Taylor = Sucks I mean I understand that weighing in at night and in the morning will give you different weights but 4.6 pounds different? That's quite a big difference.

    Edit: This taylor scale is a body fat analyzer as well but I'm beginning to doubt its accuracy.
    That's actually not too far out of the ramge of weight I see. If I weigh myself at night it's generally 3 to 4 pound heavier than I am in the morning, but the morning weight is always fairly consistent. I think the larger you are the larger the daily swing is. More water and such. I'm about 187 or so.

  16. #16
    So say we all.
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    Sessamoid: thanks for the link. I'm using the numbers as a general indication now, not an accurate measurement. Hydration definitely makes a huge difference -- bodyfat before and after a long ride is wildly disparate.

    (It seems to be measuring the trends well, though -- been hitting the gym a lot and though my weight has gone up a pound or so the BF% has been going down, so I'll just keep building the chart.)

  17. #17
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    the most accurate way of estimating body fat for the general population is by using skinfolds and regression equations (but even anthropometry cannot estimate how much deep adominal fat you have). as mentioned before, they tend to underestimate or overestimate values based on hydration levels and they have a flaw in which they assume that fat mass and fat free mass is the same density across the population
    so accuracy = no, but they can be used as a reference for weight loss if every reading you take is taken under the same conditions

  18. #18
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    Ok, to settle this matter, at least for myself, I will dig out my Tanita and measure BF% and weight several times every day, and plot a curve showing the range through a day. Averaged over a week or so.
    Should be interesting.

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