Yesterday we left off with nine folks getting weighed in on five different consumer body fat scales – all in the quest to compare it against the generally accepted more accurate method of using a Bod Pod. Some of you have asked why I didn’t use DEXA scanning instead – and the answer is simple: It was increasingly more difficult to coordinate and do at a reasonable price (it’s essentially like getting an x-ray). But hey, it saves something for the future, right? (P.S. – If for some strange reason you have a DEXA scanner in your living room and want to host a dozen folks over ‘on the house’, and are in the DC area – then I’m game!).
As I mentioned yesterday, the testing methodology was fairly simple. Each person was wearing a form fitting and as thin as possible fabric bathing suit. After each person went into the Bod Pod for their couple minutes of fame, they then hit up the lineup of consumer scales. We went down the line one by one, configuring each scale with the person’s height and age – and then recording the subsequent results.
For those scales that support an athlete mode, we did two readings – both in athlete and regular mode. The only exception to that was the Withings scale, where we did half of the folks with both metrics, but the other half with only one metric. This was simply due to people having to leave. I’ll show results compared against like types though (i.e. Athlete mode to Athlete mode, etc…). Just as a recap, the scales being tested were as follows:
– Tanita BC1000 ANT+ Scale (Body Fat/Weight – $279) – Withings WiFi Scale (Body Fat/Weight – $149) – Tanita BF-679 Scale (Body Fat/Weight – $50) – Taylor 5599F Scale (Body Fat/Weight – Target $35) – Taylor 5744F Scale (Body Fat/Weight – Target $26)
I think the best way to do this is to go scale by scale and present the results. I’ll also provide a link to the spreadsheet in the end, should you want to check out the numbers. Finally, I’ve obscured the names of everyone, and merely left it as User A, B, C, etc… There were two women, both of which were the lightest (120 pounds or less) – so those are easy to pick out. Everyone else was male between the ages of 25 and 41.
Tanita BC-1000 ANT+ Scale:
Here’s the results pane for the ANT+ enabled Tanita BC-1000 – but let me walk you through how the numbers are displayed. The upper part (in light blue) is the Bod Pod weight and body fat percentage, the lower numbers are the Tanita numbers. The section with an (A) next to it means “Athlete Mode”, and the section with a (N) next to it means “Normal Mode”. Below that we have the ‘differences’ (Diff %) between the Bod Pod body fat measurement and the scale body fat measurement.
Of course, it’s a bit hard to make sense of all those numbers, so let’s go ahead and add in the differential summaries for each mode (athlete and normal):
As you can see, on average, the difference when in athlete mode was 4.7%, whereas the median was slightly less at 3.1%. When you placed the units into normal mode, the average and median nearly flip-flopped, with the average decreasing to 3.84% and the median increasing to 4.10%. Interestingly, from a straight weight perspective – the unit was almost flawless, coming within .3 pounds for every single individual.
Withings WiFi Scale:
As we move onto the second most expensive unit – the $150 Withings WiFi scale, we continue to see similar trends from both an overall average and median standpoint.
The average for both athlete mode and normal mode was very close between 4.5% and 4.6%. However, the median strayed a bit more with it being between 3.3% and 4.4%. Like the Tanita BC-1000 scale, the Withings WiFi scale got the weight almost spot on every time. While the furthest gap was .5 pounds, it only did that once – whereas the rest of the times it was far closer for most folks, even occasionally matching the Bod Pod scale precisely. We’d see this trend across the rest of the scales as well – with almost all of them being very accurate from a weight standpoint.
Tanita BF-679 Scale
This was a generic bathroom scale that I’ve had around for years. I believe I also picked it up at a department store for relatively cheap. It had no athlete mode, it was simply a case of stand on it and get a reading.
You can see that again the average offset was about 3.66%, whereas the median was slightly higher at 4.20%. Like all the other scales, it was pretty darn good with weight measurement – which I was happy to see as I banged the crap out of this scale over the years. Happy to see that its noggin is still working.
Taylor 5599F Scale
From here we continue to get cheaper and go into the $35 scale that we picked up at Target. The only difference between this scale and the next scale that’s slightly cheaper is that this one has an athlete mode, whereas the other one doesn’t. Oh, and this one is made of pretty glass compared to the other one made of white plastic.
You can see a slight rise in the averages and medians over the previous scales. For athlete mode the average put it within 4.18%, and a median of 4.80%. Whereas in normal mode it rose to 5.36% for average, and decreased to 4.00% for the median. This scale was notable in that this was the only scale where the athlete mode was actually more accurate on the whole (both median and average) compared to normal mode.
Taylor Made 5744F Scale
Finally, moving to our cheapest scale at $26, we see that the averages don’t really stray much from its slightly more expensive brother. It should be noted that this scale does not have an athlete mode.
The average difference was 4.76%, and the median came in at 4.0% – interestingly identical to the median for the normal mode of the Taylor 5599F scale that cost $9 more. You can at least see some similarities between the body fat numbers of the normal mode between the two Taylor scales – though not as close as I would have expected.
The Average of the Averages:
The first thing I want to re-note is that the average and median values are the differences – and NOT the average body fat numbers themselves. In other words, it’s simply the difference between what the Bod Pod says it is and what the consumer scale says it is. Second, the Bod Pod has a generally accepted accuracy of 2.5%. This means that if the difference between the consumer scale is 4.0% on average, that the consumer scale could be as high as 6.5% off, or as low as 1.5%. This is a really important point. Sometimes I see people worrying about a very very tiny change – well within the envelope of accuracy – I’d suggest not worrying about such things since you may or may not have changed at all. So I’ve thrown a lot of numbers at you, but what do they look like stacked up against each other? Well…here’s some more numbers (what did you expect?):
So what do we see? Well, in general for both the Withings and the Tanita BC-1000 scale if you use the average differences then athlete mode is better, but if you use the median, then normal mode is better. What was more interesting though is that if you look at the case of the BC-1000, you’ll find that in everyone’s case the athlete mode numbers looked ‘better’ than the normal mode numbers…except for the two women. However they weren’t any more accurate one way or the other when you looked at averages.
For some people athlete mode was more accurate and for others normal mode. Virtually everyone tested here would have considered themselves athletes – most training for long events including Ironmans, Marathons, and in the case of the cyclists, century rides. Yet, the trend was that unless your body fat was either in single digits, or approaching single digits (i.e. 10%) – then the athlete mode was largely useless. For those few folks in single digits or just at the fringe, you saw the closest relationship between Bod Pod and consumer scales.
Furthermore, in the case of the Taylor 5599F scale, The Girl noticed an interesting trend in that when one changed from athlete mode to normal mode, it seemed to just smack on 4% and call it a day – no matter what the difference really was. Finally, if you looked at the differences between the two scales most folks here are interested in – the Withings WiFi Scale and the Tanita BC-1000 – you’ll find them fairly similar from an accuracy standpoint, though the BC-1000 does seem to get a slight edge by about 1% in the normal averages and .33% in the median category. They are almost a wash in athlete mode.
The challenge with all these averages and medians is that they don’t take into account the large variations on a per athlete basis. Some athletes had measurements that were off by as much as 11.4% (Tanita BC-1000) for body fat, whereas others were as close to .1% (also Tanita BC-1000). So there isn’t a simple number that I can say “It will be off +/- XYZ percent”- because you just don’t know – it could be anywhere within that range of ‘awesome accuracy’ to ‘not useful at all’. I’ve placed the entire spreadsheet here for your downloading (Excel download, view online instead). I encourage you to check it out and look at the trends (or find new ones) – it’s really interesting.
Summary
Perhaps the most important aspect in this entire two part series is the one I haven’t mentioned yet: Consistency is more important than accuracy. Meaning, if your scale consistently measures your fat at a given level and changes as you do things to affect it (increase or decrease) – that’s more important than having a one time scientific measurement that’s accurate. In an ideal world these electrical impedance scales would be more accurate. But they simply aren’t across a wide spectrum of individuals.
So what’s my recommendations? Well, get a scale that you like (be it because of the color of the scale, or its features) – and focus on one of three things: Making the number go up, staying the same, or going down. Don’t focus on the body fat number itself unless you have something more scientific to baseline it against. Yes it may be great to boast the single-digit body fat, but the reality is out of a room of really dang good-looking fit people – only two people fell in that category (interestingly, one was nearly 200 pounds).
As far as scales go – I still love the fact that the Withings WiFi scale beams my weight (which is what I personally tend to focus on more) and my Body Fat % (whatever it may really be) to TrainingPeaks. And the same goes for the Tanita BC-1000 to Garmin Connect. But that’s a choice to pay more over simply using the $30 scales from Target and writing it manually. Each person makes their own choices.
What does this mean for body fat percentages? What’s ideal? Well, it depends. There’s all sorts of metrics you can align yourself to. But for most of us that are within the healthy range, it really comes down to something more simple: Do we look good, or do we place well on the podium? To put it in perspective: The majority of the room at both ends of the body fat range regularly places on the podium in both overall and age group awards. And I’d say that everyone in the room is considered ‘attractive’ – despite having body fat ranges from 5% to 22%. Yet while all of us found the data interesting, none of us go home every day and strive to make the body fat % displayed on the scale be an exact number. Things like eating right, training right and getting rest are far more important towards our individual training and racing goals.
Unexpected Part III Here > — 
Just want to say a huge thanks again to everyone who came in and got tested. Additionally, I really want to thank the guys at CycleLife (in particular, Eric) for all the help in testing. They did this all free of charge. If you’re up for getting some tests done – I worked out a deal where if you mention my blog you’ll get 25% off their testing (nothing goes to me, it’s a simple discount for all my readers). I love giving exposure to local community bike shops like them, so if you’re in the DC area (or just visiting) – give them a shout.
[Update Note, October 27, 2015: Sadly CycleLifeUSA seems to have gone out of business about a year ago.]
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Thanks for this Ray, always wondered and now I know :)
Thanks Ray.
With respect, we all knew the Withings Body Fat scale (that you were endlesssly ‘pitching’) was an overpriced, worthless bathroom scale. The most alarming thing about your analysis is that you still recommend buying this worthless product..this despite the fact that it is inaccurate. period.
Time for you to ‘step up to the plate’ and file a public apology on your site regarding this worthless product. I will remind you that I sent you a 2001..yes, 2001 Consumer Reports analysis on the Withings Bodyfat Scale stating that the technology was flawed. Despite this, you continued to ‘pitch’ this product.
How big is your ego, can you not step up to the plate like a man and accept the fact you made a mistake.
….instead you continue to pitch the product.
Unless I see an apology and an immediate ‘pulling’ of this product, I will assume all your other reviews are flawed.
I and all your readers are waiting Ray.
I have the Withings scale and I really like it. Of course the body fat percentage is not completely accurate. It is however, consistent. Therefore useful for tracking.
Don’t really know what the RayDay dude is talking about. If he has links or research, please post. Otherwise, is seems to be anonymous rhetoric.
“2001 Consumer Reports analysis on the Withings Bodyfat Scale”
I couldn’t find anything specific about the Whithings scale, what i could find tho is the common knowledge that most of these consumer-grade scales are not 100% accurate in terms of most of their numbers.
Which makes sense, after all those are consumer-grade products and not professional medical equipment. If you want spot on measurements with as little error-margin as possible, there is no way around using professional equipment and paying the price that comes with it.
But you can’t expect to pay a meager $150 and get the full package of high-tech medical equipment, with high-end connectivity and a nice design. That’s not how the world works, because quality usually comes at a price.
These home-scales are not meant for 100% accurate measurements to replace visits with your doctor. These scales are meant as an easy way for people to track their progress and general trend, for that it doesn’t matter if the scale has an error-margin, as long as it stays around the same for each measurement.
Very interesting post! Thanks for setting something like this up!
I must say though that I don’t agree with the MakemydayRay. I don’t think Ray has been promoting the Withing scale due to it’s fantastic accuracy regarding body fat, but more so because of it’s nice integration with a number of online services. And that still stands even though the body fat measurements aren’t very accurate (I have one and my body fat varies quite a lot from day to day, but the trend _looks_ kind of right)
Ray,
Why would you want to integrate an inaccurate bodyfat number with your online services ? This is insane.
The Withings scale does not work. Period. End of story.
I think MakemydayRay might have a bee in his bonnet for a different reason. Ray has never said it is about 100% accurate results, he’s consistently stated that his recommendation for the Withings scale is that it integrates seamlessly with a number of third party producers.
My comment largely is for you, MakemydayRay: I suggest you re-read the Withings scale review and perhaps consider your comments more closely.
But for you, Ray, thanks a lot for another great blog. I loved the Withings scale review and very much enjoyed this testing – even if it didn’t really produce the results everybody out there was hoping for. But there’s a lot to be said for truth in reality!
How about a longitudinal test comparing scales vs skinfolds vs bod pod for 1 or 2 people? would be interesting to see if scale % tracks up or down for one person correctly.
Chris—the product does not work, why would you want to integrate it ?
Thank you Specialist—clean,concise reply. The problem with Accumeasure Skin Fold is its only $5.11 at Amazon and despite the fact it is relatively accurate–it does not integrate.Ridiculous, I know.
Chris–My only request is to have the product pulled and an apology.
Awsome review, as always!
As far as I could see, none of the scales you tested had upper body measuring (measuring through hands in addition to feet). E.g. like the Tanita BC-601. Would be interesting to see if one of these scales would improve accuracy.
Yes, and the Dexa Fit sounds interesting.
And of course, the nirvana of body fat measuring – A MRI scan!!
Thanks!
/Richard from Sweden
Thanks Ray,
My dad and I always liked the ‘athlete’ mode on some of those scales and wondered how the accuracy compares.
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Great work, as always. One small typo, I think. The write-up says “Secondly, the Bod Pod has a generally accepted accuracy of 2.5%. This means that if the difference between the consumer scale is 4.0% on average, that the consumer scale could be as high as 6.5% off, or as low as 2.5%.” Shouldn’t that be “as low as 1.5%” because 4.0-2.5 = 1.5? (The English curmudgeon in me also wants to note that “Secondly” should be “Second.” :)
After applying a Repeated Measure ANOVA, you’ll be happy to learn that none of the scales (in either mode) give a BF% that is significantly different (p>0.5) from the bodpod. We can assume that the different between the Bodpod and the scales is due to random chance. The only scales approaching significance is the Taylor 5599F in normal mode (p=0.09) and the Tanita BC-1000 in athlete mode (p=0.08) Some of the scales were significantly different from each other. If you are interested I can send you the whole pile of analysis.
Also interesting is that there is no significant difference between athlete and normal mode. The normal mode trends higher but non-significantly
What exactly is the difference between Athlete and Normal mode, and how will I know which one to use? I’m thinking of getting the Withings scale to track my body fat as I am undergoing a significant effort to lose a ton of weight (was up to 450, down to 350 now and would like some better analysis than just weight at this point in time).
At my weight it’s laughable to consider myself an athlete, but I exercise on average 10-15 hours a week now. I’m much faster than a lot of “athletic” people on my bicycle (however I am nowhere as fast as most serious cyclists), and I can average 15mph on my 19 mile commute to work now.
Any insight would be appreciated. I just really want something to help give me an idea of where my progress is at over time.
MakemydayRay –
Actually, your rant has proven that Ray’s methodology works. You have obviously read a review of the product on this site. You then read another post Ray made regarding that product. You took both of those posts and decided that you, personally, should not buy that product. Why would you then advocate that what worked for you – both posts being up and available to anyone that visits this site – should be changed?
Your logic confuses me, but your obvious prejudices don’t – and I don’t think they’ll confuse 99% of the regular readers of this site.
Hi Jomolungma ,
Thanks for your thoughtful question.
Keep in mind, I am a consumer advocate attempting to ultimately protect you. Protect you from spending money on a product that simply does not work.
Additionally, I am concerned for the people (such as the ‘anonymous’ person/comment above you) that are several hundred pounds over weight that will be relying on this products functionality to perhaps “save their lives”..
not so funny anymore is it Jomolungma ??
I don’t really understand what MakemydayRay is trying to accomplish, but I would like to say I bought the withings wifi scale based on Ray’s reviews and recommendation and have been very happy with it. Love the auto upload and integration with the Libra android app.
Thanks Ray,
Great posts, I’ll probably be heading over to CycleLife after reading this.
I don’t have a scale that calculates body fat partly due to not caring about it. I’ve read a lot about them and was wondering if you considered the amount of water in everyone’s bodies? As I understand, this can have an impact on the accuracy of the scale’s body fat calculation.
@Makemydayray:
Dude. Chill out. I will not be using the scale to “save my life”. I am simply interested in tracking my progress. I’m at a point where I am dropping far less pounds than I used to be, but my waistline is still shrinking. So I would like to start measuring bodyfat on a daily basis. You seem to be the only person I’ve met with an issue of the Withings accuracy. I understand it’s never going to be 100% accurate…
But to say that this thing, if it were inaccurate, would affect whether I live or die? That’s a bit over the top.
Okay, for the life of me I can’t figure out how to download the spreadsheet. The link goes directly to a viewer, and I don’t see any option for downloading. I’d like to look at standard deviations for the various scales.
Hi Specialist-
I thought about skinfold tests – the challenge is ensuring that the test practioner does it correctly (which is more of a problem than you think). My wife used to do them for high shcool kids, and was amazed at how many times she’d see others doing it incorrectly. That said, if someone offers a DEXA scan facility, I’ll get one of the more commonly used pairs and do some comparisons onsite.
Hi Anon-
RE: Percentage typo
Doh, all fixed!
Hi Nathaniel-
I’d love to see more! Feel free to e-mail me directly (click Contact info on the sidebar) so we can chat. May make for a fun follow-up post for the geeks around here.
Hi Anon-
Regarding athlete mode, it varies slightly by company – but most describe it between 10-20 hours of training/workouts per week. Which may be where we see the variations in that many of us are on the 10-14 hour range, but few of us are in the upper end of that.
Hi BriTriGuy-
Some of the scales did measure hydration levels (though the Bod Pod does not). I did actually record all of that, just for fun – it’s in the spreadsheet details if you want to take a look. They were pretty consistant across scales, but we have nothing more detailed to compare it against.
Hi Stephen-
I’ve added a second link to go ahead and either download directly, or view in the online Google Docs sheet. Let me know if that helps out! (Just refresh this page to see the link in the original post).
Thanks all!
while I do not share the tone and insistence of MakemydayRay, and as the owner of one of the tested scales, I think the accuracy of the scales in terms of body fat percentage is low to the point of being meaningless.
You should also take into account other factors that vastly affect the readings such as the time of the day or if you’ve just had a shower or are sweaty, to name but a few, to complete the test.
In the end they are only partially valid as Ray says to track changes, and I would say only long term changes. I can change from 14% to 17% on consecutive days.
While I do agree with the critic that it is absurd to be able to send useless data be it via Wifi or ANT+, I appreciate the article for bringing further proof to what I already suspected.
Hello,
Nathaniel’s post is interesting, and completely testable! Consistency is really the key over repeated measurements.
I’d just like to add that the standard deviation (which tells you about variation of the data) of the difference in body fat % between the BC-1000 and Withings with respect to the Bod-pod (which is a really cool name) comes in at:
BC-1000
Athlete mode = 4.3
Normal mode = 1.9
Withings:
A mode = 4.6
N mode = 2.1
Which would suggest the normal mode seems to work better across individuals then the athlete mode, given that the means (average difference) are so close.
Anyway, the dataset is so small, we can’t really say anything about the scales from a scientific point of view.
So as Ray says, pick the colour you like! :-)
MakemydayRay’s posts suggests (in a not so polite manner) that the Withings is not accurate. On the face of this data along, we can say that its about the same as the BC-1000, measuring the difference across individuals. Whether or not for a single individual its not very accurate, we can’t say that from this data because it wasn’t tested for. I don’t have any of these scales so I defer to MakemydayRay’s experience.
opps “along” = “alone”
Great to host the experiment for you, Ray. Look forward to any follow-ups and as well as seeing some of your readers in for their very own BodPod experience.
really good series.
Hi Ray,
Have you heard of the Bodymetrix device? I and I know many others would be interested to see a similar accuracy comparison between BodPod and Bodymetrix (ultrasound).
Thanks,
-Adam
Would have loved to see the Omron BF508 in the mix. I have it for a while and it seems to be at least pretty consistent and somewhat I hope those Japanese Engineers really pulled something off with that additional handle.
Am I understanding your readings correctly- you make the point that these measurements vary by 3-5% or so … but since the readings are in the 8-15 points range – that translates to a 30-50% variance.
Looking at users A and B. Apparently they have 9.7% difference in body fat. The biggest difference given by the scales is 2.1%, one even says that user B has less fat than user A.
Does that mean that if user A loses 9.7% body fat it will only measure a 2.1% difference? Does user B strive to lose more weight as they think they are 11% fat, whereas they are actually 5.9% fat?
It seems a bit pointless. I would guess that the jiggle test would be more accurate! (jump up and down in front of the mirror – how much do you jiggle?!)
Richard, I think many of you are missing the point. There are many physiological differences between individuals that will likely give rise to relatively consistent offsets to true BF% when using this method. One guy may have a higher natural electrolyte profile than another. You could pay for 1 BodPod reading and then assume some sort of reasonable delta to these scales and get pretty reasonable results in tracking increases/decreases in your own BF%. Obviously it makes sense to weight yourself at the same time of day with a similar hydration level…to keep the results most consistent. I use my scale in the morning after using the restroom and have very consistent results over time.
To the author, I also would love to see a hand/foot scale thrown in as well. Omron/Tanita make them and are ideally more accurate for individuals that store more/less BF in different areas of the body that foot only would miss. You could also through in the Omron hand to hand meter which is very common in gyms.
Thanks for the nice tests!
The top, most expensive tanita is much more accurate than quoted in the results section. The scale pretty accurately hits people that should be in the athlete group when tested as athletes, and the people in the normal group got accurate results when tested in normal mode. So, what are the qualifiers to be an athlete? I can’t see a trend between the weights and body fats to see who goes where. Maybe the only way to know is to bodPod it and compare your number to tanita normal and tanita athlete. Sounds kind of $$$…
Hi Ray – I have the Withings WS-50 scale and I’ve always wondered whether I should be using the “athletic” mode or the “normal” move. Withings’ own guidance says that if you work out more than 8 hours a week and have a resting HR of below 60, then you’re athletic. Otherwise, you’re normal. Well, I work out for *about* 8 hours a week and my resting HR is *about* 60 so I’m right on the fence.
So I set out to repeat your testing for myself – like you, I used a BodPod. My results as follows:
Withings – athletic mode 8.2%
Withings – normal mode 18.5%
True percentage (BodPod) 14.7%
Pretty disappointing to be honest. Not sure how to interpret this. Maybe it would be more accurate if I was more obviously either “athletic” or “normal”.
By the way, it’s worth stating that from a weight measurement point of view, the Withings was spot on – agreed with the (highly accurate) BodPod scales down to the decimal place – 171.7 pounds.
In the end, I do agree with your conclusion – absolute accuracy is not as important as consistency since the day to day trend is the important thing. So no plans to give up my scale.
But still disappointing.
Best I can tell, Athlete mode is really for people that are hitting those low ends of the bounds as it is (ie BodPod around 10%) rather than the workout metrics they list.
I am well behind the times with this conversation but for those interested in BodyMetrix or ultrasound to track changes to B%F and muscle here is an independent comparison between the two link to aahperd.confex.com
*Please note, were the UK Distributor. I am not trying to sell just supply information above.
I found this scale and am really liking it. It will save your weight and also has a tate function. works well for us
Great article Ray. I plan to do a similar study soon with a larger sample size with about 50 people and 10 different consumer scales.
For now I hope you don’t mind me using results of your study for now in my body fat analyzer guide. I will be of course link back to the source :)
Really amazing post. I’m so glad you’ve done these reviews. I’d love to know how much you’d recommend on spending or what specific model is good enough to measure water loss after runs to some degree of accuracy.
Do the $30 ones work well enough or do I need something like the crazy expensive Garmin one.
Not that fussed about it being wifi or “smart” but if that only comes with the really accurate ones, so be it.
Would love to know your thoughts.
T