John has mentioned the Health Central body fat test in his postings..

http://www.healthcentral.com/cholesterol/home-body-fat-test-2774-143.html

Get this..

I enter in my data:

age 30, male
weight 178 lbs.
waist 37
hips 38
forearm 12
wrist 7

It says 13% body fat.

I change my age to 31 (I turn 31 in a month and a half), and enter the same values.

Suddenly my body fat is 16.6%

What a joke!!

John has mentioned the Health Central body fat test in his postings..
So what? I didn't endorse it. I merely mentioned in my FAQ (http://www.johnstonefitness.com/php/faq.php#0380)that I used it (along with two other methods) back in 2003 for the first 8 or 9 months of my transformation before switching exclusively to calipers.

So what? I didn't endorse it. I merely mentioned in my FAQ (http://www.johnstonefitness.com/php/faq.php#0380)that I used it (along with two other methods) back in 2003 for the first 8 or 9 months of my transformation before switching exclusively to calipers.

So nothing. It's a point of reference so people know what I'm talking about and where I heard about it from. I'm not implying anything. I wouldn't expect you to know that the thing is buggy. I didn't know until yesterday when I was playing around with it. Before then I assumed it was within a few points of accuracy and had used it many times.

I posted this so other people know to stay away from it. Gaining 3.6% body fat because I have a birthday makes no sense at all.

So nothing. It's a point of reference so people know what I'm talking about and where I heard about it from. I'm not implying anything.
Mentioning where you heard about the Health Central body fat test wasn't in any way relevant to your point. So, dangling that statement out there with no further explanation--especially right before you railed on the site--may have left some readers with the mistaken impression that I've somehow suggested that the Heath Central body fat test is an accurate means of determining body fat. I have not, and I wanted to clear up any confusion that your ambiguous statement may have caused.

Sorry! My mistake!! :o

I have to say I'm familiar with the Health Central Body Fat tester and I can tell you it's similar to one in the late Covert Bailey's Fit or Fat series of books. I find it interesting that you went from age 38 to age 31 and got a different reading because as far as I know the bf% test has diffferent readings for under 30 and over 30. I know this because I developed an Excel spreadsheet based on the measurement used in the Health Central test. I didn't like their test because I couldn't get the degree of accuracy I wanted. The spreadsheet I made allowed finer degrees of accuracy in the measurements.

One more point to be made that was overlooked. Bodyfat % isn't an exact measure, unless you do the underwater test. But as a way to make a consistent measure of progress, you can get a good idea of where you are going. No one is going to change from 38 to 31 in a short time. So you're reaction was not a measure of anything in reality. Remember it's only a tool, and tools can be useful when making consistent measures over time.

For a link to the thread with the spreadsheet go here. (http://forums.johnstonefitness.com/showpost.php?p=327273&postcount=1)

No one is going to change from 38 to 31 in a short time.

lefty,

You may want to check the ages the OP used again...either your eyes are deceiving you or mine are...because I see 30 to 31...which is a change people actually do in a matter of nanoseconds ;)


Bodyfat % isn't an exact measure, unless you do the underwater test. But as a way to make a consistent measure of progress, you can get a good idea of where you are going.

banderbe,

lefty is right on this. Any generic computer application is going to be based on approximations and it would be completely understandable for an application to make new approximations when an age crosses a line. Whatever method you used to predict the 12% you claim in your stats also contains flaws...unless you used submersion.

The fact is...the site is now claiming you have a whopping 6.4lbs of additional fat spread over your 178lb frame. Not all that much when we're dealing with approximations anyway. I know it may be a shot to the ego for the number you track progress from to now be higher...but it doesn't really matter. You can still now monitor your up or down based on the approximations for the age group you're now in. Most likely...the lower number you were getting when you were in the 30 and younger group was off anyway too as you approached 31 (assuming that IS where they drew a line for their formula).

I know John didn't endorse it...and I'm not either. I'm just saying that any tool that can give consistent approximations of upward or downward BF% movement when non-body-comp variables are held constant (like age)...should be useful for monitoring up or down progress. Even if it does mean an ego hit when the "baseline" is higher than we'd like.

the bf% test has different readings for under 30 and over 30.

Why?

Does our fat hide in different places as we age that are not measured by those girth measurements? Do our bones get less dense? Do our organs grow or shrink? Does our blood volume change? Does our skin get thicker?

I've never found any girth measurement calculators to be anywhere within even 5% points of what I believe my true body fat percentage to be. I'm lean in my arms and abs, and fatty in the hips and thighs. I think my scale probably overestimates my body fat as well, because the calculation is based on the current running from my foot up my leg, across my abdomen, and down the other leg to my other foot. Since my lower body is fattier than my upper body, I don't think it's a very accurate tool for me.

The underwater test is just an approximation as well. In-vivo neutron activation (http://en.wikipedia.org/wiki/Body_fat_percentage) would give you the most accurate number, but even it could be off by a few fractions of percentage points.

I am almost positive that for the first two years I tracked my body fat percentages, I was wrong. Off. Not correct.

But I *was* consistent in my measurements, which gave me a relative measure of how my body fat decreased over time, which is really all that matters for the purposes of data collection and later, analysis of the information.

I understand that during the initial phases of physical transformation, everything appears to be of the utmost importance, body fat measurements especially. However, you shouldn't be so hung up on accuracy; your exact body fat isn't all that important. Tracking how it decreases in some consistent, relevant manner is. Later, if you track your diet as well, you'll be able to tell when you lost fat most efficiently, what your dietary intake was at the time, and you can later duplicate and/or experiment with that training information to improve your body composition.

-R

Does our fat hide in different places as we age that are not measured by those girth measurements? Do our bones get less dense? Do our organs grow or shrink? Does our blood volume change? Does our skin get thicker?

Yeah actually several of those things actually happen.

That doesn't make the health central calculator good though.

There is probably a simple mistake in the calculation. Whatever statistical analysis that led to the formula in question is not likely to have used quantized ages - or if it did, they would likely have applied a "continuity correction". So if this was done well, you wouldn't get a discontinuity across an age boundary, and you wouldn't notice this issue.

That still wouldn't make the formula that useful for individuals though. Those formulas have errors for individuals which more or less cancel each other out when you add up the results for a lot of people - they can be quite accurate at predicting the total for a large sample. The trouble is that none of us is a large sample.