A friend of mine mentioned she was in a weight-loss doctor’s office recently. In the office there was a scale that not only measures weight but could calculate what percent of her body is fat and what percent of her body is water. How does this scale work? She said she only had to stand on it in her stockinged feet and it printed out the stats in a digital format. I tried to google for info but without the name of the machine I couldn’t find out much.
Thanks.
IANASE(scale engineer) but I saw one at the mall (and people could try it and then discuss with the lady about health stuff) ; however, the lady at the mall claimed it worked only if you were barefoot.
This is just a WAG but I think it must be scanning your feet somehow and then making an approximation for your whole body based on the fattness of your feet and your weight…
It measures the electrical impedance of your body, and figures the time it takes the signal to get from the scale and back to the scale and then estimates your body composition. The water thing complicates this process, with athletes’ muscles’ water content throwing the measurment off on the upside for bf. If you are wearing clothes, it will be off too, for some/most scales.
Do a search on “Tanita” – for a while now, it’s the only brand that I knew of, and I’ve just recently seen other makers enter this market (for consumers, anyway).
My very sketchy (and probably wildly inacurrate) understanding is that it sends a pulse through your feet and measures the resistance – evidently water/muscle/fat each give different values – which is why you need to be barefoot. And (purely IMO) unless the results are interpreted by a professional, I’d take them with a grain of salt – for example, one of the Tanita scales has both a “regular” and an “athlete” setting, and depending on which one I used, the numbers are pretty different – I’m certainly no marathoner, but I’m no couch potato, either, so which number to use?
There are paper “scales” on the internet and in books that will give you a body fat percentage by taking the data from your skinfold measurements and plugging it into an algorithm with height, weight, age, etc.
Obviously this is not the kind of scale you were talking about, but it’s the one the guy at my gym uses for my fitness assessment every couple of months.
As mentioned, the real thing measures the electrical impedance of your body, and from that can determine the percentage of fat based on the amount of body water present (fat has almost no free water). Be wary of the many companies that market scales for about 100 bucks that mention electricity but really are only giving a very rough ballpark of your fat percentage by taking your weight and info you input about height and gender and are no better than just looking it up in a book.
Fuel and Earthling are correct. We have a Tanita scale at home, and according to the manual it measure electrical resistance through your legs. You have to program it for each person in the household (age and height) and push (kick, actually) the button for your program before you get on. It takes a few seconds to measure and you can feel a slight prickling sensation as it goes to work. Omron also makes a hand-held model that works the same way (though obviously it doesn’t measure your weight).
Personally, I don’t think they’re accurate enough to be worthwhile. From the day we bought it, it’s measured my body fat as between 25 and 27%, whether I’ve had folds of fat hanging off gut or whether (like now) I’m actually able to see my abdominal muscles again. According to the scale/fat meter at the gym (which measures from the feet and hands together and shows percentages and distributions of fat, muscle and water) my body fat’s steadily gone down from 20% to 12%, but the scale at home still says I’m 27%.
I just googled Tanita and what I found was that all but their two or three high end professional models are bullshit, using the weight and gender to calculate BMI and pretending to measure electrical impedance. I bought a similar fake model from sharper image. I am fat, but my kids are not only in great shape but athletes. By changing the imputed gender and height I could make any of us seem thin or fat. My son had within the past month had his body fat measured by the immersion process and had a known 5% body fat, but because he is muscular and muscle weighs more than fat the $100 dollar scale had him pegged at 18%. I returned it.
Also not that to measure the impedence of your body the electricity has to travel somewhere. There needs to be an electrode on your upper body and a measuring electrode at the feet. Anything that you just stand on, even if really measuring impedance, could at best measure your legs only and just estimate the rest.
hmm… that could explain the results I was getting with mine.
Yeah, but don’t they only measure body fat on the lower part of the body? & as Sublight said, they aren’t very accurate. Still might be better than nothing.
I have a $100 sharper image scale that has the weight and height, gender inputs. The measurement is way off, especially since I am an athlete, BUT the measurement is highly precise. So, I can tell changes in composition from this scale very well. So, as far as i’m concerned, it’s still worth the money.
Unless yours is a hell of a lot better than my $80 Tanita one (which is no good), the reading can change quite a bit based on how much water you’ve had recently, and how recently you’ve taken a piss. Try sucking down a couple glasses of water and measuring yourself again. If it’s close, you have a good one.
OTOH, I know mine isn’t just doing a table lookup because I can cut its bodyfat reading in half just by wearing socks.