Body Fat Monitor Question

BossArky

About 6 months ago I did a body fat reading in the local gym using the following body fat monitor.

http://www.martinrothonline.com/personalhealthmonitor/images/Omron%20body%20fat.jpg

The results were roughly 14 to 15% body fat and just over 25 BMI.


A few weeks back I bought a body fat monitor on ebay for £10 (they are also available in a London pharmacy (llyods??) for the same price). Now this body fat monitor gives me a body fat reading of 22% and BMI of 25.

Fearing that I was turning into a marshmallow man I went to another branch of the original gym and used their hand held device (same as initial link). Again I got readings of 14 to 15% body fat and BIM of 25.

Why do the different machines give such different readings (body fat of 14 or 15 Vs 22, whilst the BMI stays the same). Is it because the one I got on ebay does not take muscle into account?

By the way, I'm 25, male, 5 foot 7, 74 kg.

g'em

Those electrical impedence bf monitors are notoriously innacurate and there's all manner of different things that can influence the reading- your hydration levels, how recently you worked out... and more often than not the readings they give are just plain wrong. Calliper readings are a better measurement of body fat, but not perfect. By taking skinfold measurements though it's an easy method to track your own progress (the skifold either gets bigger or smaller, pretty simple!!). You can pick up callipers reasonably cheaply from lots of the on-line fitness stores.

Your BMI is jusdged on a height: weight ratio with no differentitation at all between muscle weight and fat weight, so you can maintain the same BMI but with greatly varying degrees of body fat.

BossArky

Yes, I know how the BMI is calculated and also that body fat readings vary depending on when they are taken and what you have eaten recently, etc. That is why I averaged a number of results and came up with "between 14 and 15%"... (exact readings were 14.5, 14.6 and 14.8).

What I want to know is what exactly is the reading that my home fat monitor is giving me? Is there something else apart from %body fat and BMI?

Maybe it is just a cheap piece of junk.. but I wanted to be sure before dumping it.

So, what other reading is there, if any, that could be approx 22, whilst my bodyfat is 14-15 and BMI is 25?

g'em

BossArky wrote:

So, what other reading is there, if any, that could be approx 22, whilst my bodyfat is 14-15 and BMI is 25?

the number of biscuits you ate that day? the chart position the Sugarbabes entered with their new song? Your IQ?

I kid, I kid. The 22 is the machine's reading of your body fat, but if you have a BMI of 25 (normal) and you're in reasonably good shape, then it's probably wrong. I wouldn't pay any heed to it at all really. The 14% readings are still coming from an impedance measurement type machine, but it may be a little more accurate if its one of the Tanita style ones. If you still want to know your bf more accurately get measured with callipers.

rubadub

Did you use your own monitor immediately after the gyms one? Your readings will change by the hour with these monitors.

Perhaps you were at the same level of hydration in the gym both times.

Fearing that I was turning into a marshmallow man

A mirror will tell you more than those monitors.
I am surprised that a gym would actually use them seeing as they are well know to be crap.

I have a cheap calipers, it is called slimguide, it comes with a spring so the tension is the same each time, if you get a hand calipers you can squeeze harder or lighter and get varied readings.
You measure various parts on the body and put the figures into a formula, but formulas vary some say I am 8% BF some 20%!.

Thing is to ignore all that, just keep track of the figures in mm. So I am 26mm when I tot up 5 areas, if I am 24mm the next time I know I have lost fat

BossArky

Yuppa, I cross referenced my own monitor a with the gym's monitor. It looks as if my own monitor is a tad dodgy. (They both give consistent readings in their own right...)

I shall take a look at some callipers. Any in particular that you recommend?

rubadub

BossArky wrote:

Any in particular that you recommend?

After reading up on a few forums these were the most recommended

http://cgi.ebay.com/New-Slim-Guide-Body-Fat-Caliper-with-Measurment-Guide_W0QQitemZ180081828578QQihZ008QQcategoryZ44078QQssPageNameZWDVWQQrdZ1QQcmdZViewItem

The spring means consistent reading as I mentioned.

I got mine here
http://www.fwonline.com/cal.htm
but they were on offer at the time, I think ebay would be cheaper now.

I_and_I

What is your waistline measurment?

BossArky

32 inches.

g'em

BossArky wrote:

32 inches.

hehe, we have virtually identical body measurements ('cept I have a smaller waist ). No idea why I pointed that out.. it's one of those mornings...

I_and_I

Is that your trousers waist or in between your hip bone and last rib waist (around navel height)?.

With these measurments.
Estimate #1 based on height and weight
Your "Ponderal Index" is 12.27 which gives an estimated body fat of 28.4% (46.3 pounds of fat)

Estimate #2 based on waist size and weight
Estimated body fat of 12.9% (21.0 pounds of fat)

But honestly the only method I would trust is the one where they weigh you underwater it is the most realistically accurate method.

Just for contrast I did my own which ends up at (185lbs/6ft2/35inch waist)

Estimate #1 based on height and weight
Your "Ponderal Index" is 13.01 which gives an estimated body fat of 13.3% (24.5 pounds of fat)

Estimate #2 based on waist size and weight
Estimated body fat of 17.3% (31.7 pounds of fat).

So I don't really know what to make of its accuracy.

Dragan

With regard to bodyfat I suggest the following formula to work it out and then decide your course of action

Step 1 : Remove clothes
Step 2 : Look in mirror.
Step 3 : Decide if you feel a) happy or b) unhappy with what you see.

If Step 3 = happy then relax, else put down pie and head to gym.

BossArky

I_and_I wrote:

Is that your trousers waist or in between your hip bone and last rib waist (around navel height)?.

That is my trouser waist.

Once I get my hands on some callipers, and the callipers on my flab, I shall report back for the sake of comparing the calliper reading to the others mentioned above.

davyjose

A couple of weeks ago I stood on mine and took my bodyfat measurement. Three seconds later - having changed nothing - I moved my feet to a slightly different position (not cheating, my heel and ball still covering the pads, weight was the same) and my bf% dropped by a whole 2% - that was the last time I will ever use it.

I_and_I

Throw the tape measure up around your navel and tell me what is says.

rubadub

BossArky wrote:

That is my trouser waist..

actual waist, or jean size? I have a 34" waist around trouser or above navel, yet wear 32" waist jeans and can pull them down over my hips without a belt on.