Reviewing my WiScale Experience

Posted by

Since I mentioned the WiScale a few weeks ago, I figured I’d report back on how I like it. So far, I’m really enjoying stepping on the scale in the morning and not needing to remember to log my weight, but the scale is certainly not perfect. I’m reasonably convinced the weight measurement is both accurate and consistent. I periodically compare my weight on the WiScale to my weight on another scale and they are always within 0.1 pounds, which seems reasonable since I’m guessing each one rounds differently. The BMI measurement also seems to be consistent from day to day. On the other hand, I think the fat percentage measurement in the WiScale is largely inaccurate.
Take for example the most recent 3 measurements of fat in pounds. Saturday put me at 25.8%, Sunday at 26.1%, and this morning I dropped to 23.6%. The first two numbers I find plausible. The third number is where I get suspicious. Apparently overnight I lost 5.5 pounds of fat, while my weigh in shows me 1.5 pounds lighter. These discrepancies pop up on a regular basis and I find it hard to believe that I’m magically melting off fat one day only to have it reappear the next. I weigh myself at approximately the same time every morning on an empty stomach, so this isn’t a matter of my food intake, liquid consumption or anything else throwing off the scale.
I guess that’s a fairly long way of saying I think the fat measurement on the WiScale isn’t particularly accurate. I do stay in the same general range from day to day, but I can’t find any supporting evidence online to suggest the types of fluctuations the scale is measuring are common, which leads me to the conclusion that the scale isn’t measuring that particular data point with a high degree of accuracy. We shall see if it measures a trend up or down over time within the range or not. If you want to keep track of your health data in a more automated fashion, I still recommend the WiScale as a great way to record several data points to watch for trends, because even inaccurate data can reveal patterns over time.
Do you have experience with the WiScale? I would love to get your feedback.

Advertisements

4 comments

  1. I’ve been using a Tanita scale for 7 or 8 years, which does weight and fat %. I’ve done comparisons of weight with another electronic scale that my wife uses, and they are quite close together, within 0.1 and 0.2 lb.
    I have no way of comparing the fat % with another scale (unless I buy one) but like you, I have noted great variations from one day to the next. (It is also possible to have weight variations of several pounds from day to day, depending on you sodium intake, water retention, and just where in the daily elimination cycle you weigh yourself.) However, there are also great variations between fat % measurements taken literally seonds or a few minutes apart, without “doing” anything in between.
    Since the fat % is determined by an impedance measurement between the soles of your two feet, anything that changes the resistance between your feet and the pads you stand on will change that impedance. Simply taking two measurements in succession does that; the first measurement leaves a film of body oils on the pads, which chnges the resistance for the nest measurment. You step on the sclae for the first measurement from the floor, which has on it some deposits, osap film, dust etc., step off the scale onto a different part of the floor or onto a bath mat, step back on, and the resistance has changed.
    I have not experimented with cleaning the soles of my feet and the pads on the scale with alcohol before and betweet measurements, but that might lead to more consistent readings.
    The moral of the story is that fat % measurements are not absolute. IN order to get any meaningful feedback on the effects of exercise, diet, etc., you need to keep a weighted running average off some number of past measurements (the further back, the less weight) and then look at trend. How many measurements to include, and what the weights should be, is another problem, and I suspect one that no one has done any research on.
    For what it’s worth, any kind of biological measurement is subject to these kinds of variations. I use two other measurement devices, a glucometer for tracking blood sugar, and a very expensive $1000 for the device and about $7 per measurement blood coagulation time meter. Glucometer readings can be all over the map, even for readings seconds apart; 1) natural random variations in the device and the test strip. 2) blood sample taken from different fingers, or different places on the same finger; or even from the same finger stick as the act of puncturing the skin causes changes in the blood and serum seeping from that tiny puncture. I you look at the litereature, variations of 20% are not unexpected. The blood coagulation meter is somewhat more consistent, but even here there are external factors that can cause relatively large variations in successive readings. In addition to the above, I have noted that, because of the way coagulation time is measured, varitations in vibration level on the meter are important – eg. don’t measure on an airplane. Even at home, if the amount of traffic past your home varies between measurements, it can have an effect.
    Final word, biometrics are notoriously difficult, because of the number of , often random, external influences. Lab results, incidentally, are no better, in fact, can be worse, because the number of random influences multiplies with transport of a sample to a lab from a collecting station.
    The moral; only averaging of multiple measurements over time, or multiple measurements at the same time (look up “ergotic theorem” in a statistical text) will give meaningful and accurate information.
    (Which is why I am ticked off and continue to argue with my physician, that, at least up here in Canada, a single glucose tolerance test that is 0.1 units (about 1%) over a magical number labels you as a Type 2 diabetic.)

  2. Jake –
    Forget the body fat measurement. No way such a device can give you an accurate measurement. I think the preferred (accurate) method still involves a flotation tank, but I may be behind the times on this one.
    I agree with other posters about daily fluctuations in weight measurement. My weight seems to naturally vary up and down as much as 2.5 pounds a day. In other words I can go from plus 2.5 one day to minus 2.5 the next.
    Because of this the standard advice is always to “weigh yourself once a week”. An illogical response if you ask me. How do you know on that one day if you are hitting a “heavy” day or a “light” day? I think this advice is giving out so dieters won’t get discouraged by daily weigh ins. But if you are on a diet and lose 1.5 pounds over a week (a nice result), the daily fluctuation can mask this. So the “once a week” answer makes no sense to me.
    I weigh daily and take the average once a week, on the same day of the week. I think that gives me a more accurate reading of my “real” weight, as it more or less eliminates the daily fluctuation as a factor. In addition, because of daily fluctuations, I don’t consider that I’ve arrived at a target weight when dieting unless I am at or below that target 2 days running.

  3. I’m a personal trainer. I do not have experience with the Wi, but I can tell you now, that any method other than hydrostatic weighing or skinfold caliper (by a well-trained individual) will not be accurate. Bioelectrical impedance tends to be very inconsistent and can be affected by humidity in the environment, among many other factors. You are probably considerably lower than the Wi is telling you. I have a feeling you’ll hear many responses like this one.

  4. What Gerry has said above is correct – it’s a calculated value that has more to do with hydration status (among other things) than actual body fat. It will vary day-to-day, but over a few days, these changes will average out.
    The discussion above seems to be about about “accuracy” – getting a number that actually reflects your body fat percentage every day. It’s not “accurate”, but it is “consistent” – you’ll get approximately the same reading if you test yourself every minute for five minutes.
    With all that said… Consider what you’ll DO with the numbers.
    My guess is that you’re wanting a numerical reassurance that your days/weeks of behavior change is paying off. I graph my bodyfat numbers daily and then look at the TREND rather than the number. When I see the line trending down over a week or two, that provides reassurance that my diet and exercise initiative is having the desired impact.
    If that’s what you want, consider looking at the numbers graphically over time and celebrating your success rather than inspecting each day’s number and producing doubt.

Comments are closed.