When I last got a number of performance tests done at the Surrey Performance Institute one of the measurements they did was body fat analysis using callipers. When I got the results I realised there was a little bit more to know that just the numbers. Hopefully this post will be useful to some of you who are aiming to lose weight and want to use body fat as a gauge. I’m planning on it helping me too by hopefully cementing my understanding through the act of writing. ;^)

Back Story

My interest in fat (or more specifically the removal of fat from my body) started out being measured simply by weight. I wasn’t obese but I had enough extra pounds to lose that weight was a “good enough” measure for body fat (its directionality not a specific number). To top up my knowledge I was using the Withings Body Fat scale which quickly and simply allowed me to gather and tracking weight and body fat. I knew the critics complained about the accuracy of body fat measurements through an electrical resistance based sensor (as is employed by the WIthings scale) but it’s simplicity and my lack of dependance on precise results made it entirely acceptable for the timeframe. This year I realised that all the “easy pounds” were gone and while I could probably still use weight as a crude proxy to body fat it was becoming less effective to measure my success/failure at losing body fat.  Enter stage two … the Calliper era.

Body Fat Measurement with Callipers

The only true and absolute way to measure body fat during an autopsy after your dead and to many people that’s not an attractive trade-off to achieve this level of precision. The second most precise method (I believe) is through water displacement and while you can do that the facilities required are quite costly and hard to come by (at least in the UK). That leaves the “calliper” as the gold standard amongst those who are interested in continuing life and living within practical boundary conditions.

Great. So why aren’t we all using these simple devices? They’re small, they’re not that expensive (although good ones are). Yet almost no one I know has measured themselves with Calipers and according to Sports Fitness Advisors that’s a good thing. It’s good because these are precise measurements where .1mm makes a difference and if you don’t measure in precisely the right spots you’re getting the wrong answer.

Ok, so that means it requires skill but that’s not all that makes it difficult. In the end we’re all still just simple cave men that have traded in our caves for houses. We like information in small packages. When Withings tells me my body fat percentage is 16% that’s an easy number to remember. For many of you, if told that your body fat percentage isn’t “a number” but “many numbers” your heads will explode. Maybe not your head specifically but someone you know’s head. I’m sure there’s a scientific study somewhere that will back me up. Anyway, when a data set grows larger from a base of 1 the complexity of understanding and internalising it move up exponentially. What can we do? Can’t we just get back to that single number somehow? Well yes and no. There is clear demand for a single number that is headed up by the vocal cave man lobby and in response many formulas have been developed through the years to do just that. Six of the most common formulas are listed below (thanks to linear-software for their cool online tool … you can find it here: http://www.linear-software.com/online.html):

Voila Capture96

The cave man (or woman) inside of you is clearly pleased. All those numbers were a distraction. A facade. You don’t need them as you now have formulas that will get you back to beloved single number. These are indeed happy days but wait … there’s a rain cloud on the horizon. What happens if you put your data into these formulas? Well shock and horror … they produce different results. Wildly different in many cases! How can that be? Well the reality is the various formulas have to assume certain things that aren’t static in the general population. Variables like age, ethnicity, athletic conditioning, gender, and many others will effect the effectiveness of these various formulas. To illustrate this here’s a sample variation I found on Sport Fitness Advisor:

Voila Capture97

That’s one big standard deviation. Big enough to end the cave man party that you were planning. What do you do? Well what’s typically recommended is stop using these formulas. Start coming to terms with the “set of numbers” rather than “just a number”. Doing this will mean you’re learning more about your overall body and you no longer need to worry if you’re using the right formula because there’s no formula needed. The only problem is … it’s a lot more work and it will take a bit of time before you can look at these number and have them intrinsically mean something to you. What’s best for you is an individual choice. Personally I’m going to try and do both and see which one sticks over time.

One last note, i have been told that the Durnin and Wolmersley test is by far and away the most popular formulas in use and while popularity doesn’t always point to “better” it does immediately make it more “referenceable” which helps contextual and communicate your numbers to others.

Measuring at Home

As was already mentioned, measuring home in a meaningful way requires precision and many would suggest just having this handled by professionals. However I suspect many of you reading this are quite keen on doing it yourself anyway. I’m in this camp and although I haven’t started yet I have bought a calliper that is recommended for home use: the Accu-measure FatTrack digital calliper system. I’m looking forward to building the courage/patience to start using this somewhat regularly but would be interested in others view on this device if they’ve used it before.

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  • Ian

    I did callipers for a while; but the difficulties of consistency made me move on.
    I now use a Tanita body composition machine. I’m not sure if it is more accurate, but I do think it is more consistent. It is easier to do. I do it daily; and I also graph a running average over 7 days to further iron out noise.
    I am more concerned with how my body comp. is changing than absolute measurements.

    • http://ken.net Ken Snyder

      Are there any particular ratios or aspects you’re focused on? The guys at the Surrey institute said they thought this was important but when pressed they didn’t have any good examples which is a shame as I’d love to look into this a bit too. I guess maybe it’s a litte more instinctual and less strict ratios. What do you think?

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