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BIA-Bielectrical Impedence Analysis, Flawed Devices.
KennyCrox posted:
BIA is an acronym for Bioelectrical Impedence Device. "This technique uses a machine that sends harmless and painless electricity through a person's body to "weigh" each of the different kinds of tissue in their body."

The Wedmd articles goes on to incorrectly state, "BIA is very accurate..." Nothing could be further from the truth. The BIA devices sold in the stores are incredible inaccurate when it comes to measureing you bodyfat.

Personal Prespective

I've seen the inaccuracy from the perspective of working in a retail fitness store that sells them. I've never sold one myself but I have had individuals buy them from me.

The distinction of selling vs buying them is that, selling indicates that I advised a customer to purchase a BIA based on my knowledge that the BIA is a good investment. It is NOT.

Buying one from me, pertains to an individual's decision to purchase the BIA, after I have educated an individual as to the inconsistance of the BIA.

I have seen those inconsistencies in the BIA as a personal trainer. The fluction in the bodyfat percentages drive people up the walls.

Let's Look At Some Numbers

As an example, let's say you weight 200 lbs. Your bodyfat percentage one day is let's say 20%. The next day, which often happnes, your body fat percentage is 22%.

That means gained 4 pound of fat in 24 hours. The next day, your body fat percentage might be 18%. That would mean that you lost 8 pounds of fat in 24 hours.

So, which reading is the right one? The answer is that you don't know.

The only thing consistent about the BIA is it INCONSISTANCY. The inconsistency is makes it very confusing.

Some of the inconsistance has to do with your hydration level. Upon waking, your are a bit dehydrated. Thus, it will show that you have more bodyfat than it does.

Also, if you have eaten, exercised or showered/bathed in the last few hours, it skews your bodyfat percentage reading.

BIA Models...Scales or Hand Held...More Problems.

Another problem with BIA devices is they are Site Senstive. That means the BIA is most senstive to where you make contact with it.

Scale BIA devices that you stand on, tend to be skewed toward your lower bodyfat percentage. If you tend to store bodyfat in the legs and hips, as most women do, then the Scale BIA will indicate that you are fatter than you really are.

Hand held BIA devices are skewed toward your upper bodyfat percentage. If you tend to store bodyfat in the arms and chest, then the Hand Held BIA will indicate that you are fatter than you really are.

"Also reducing the reliability of this method is the variation between models of the BIA devices: for instance when comparing outputs from a Tanita scale to an Omron Body Logic handheld device the Tanita scale overestimated the percentage body fat in college-aged men by 40% and in college aged women by 55%." Exercise physiology: Basis of Human Movement in Health and Disease, Second Edition, Lippincott Williams & Wilkins, 2006

Kenny Croxdale
girlinbackrow responded:
Infrared devices are even worse. What are your thoughts on the Pod?
KennyCrox replied to girlinbackrow's response:

I am not familiar with the Pod to provide you with my input. However, I question the accuracy of all of the devices used.

"How Good Is the Bod Pod?" states that it is shown to overestimate body fat"026

I've tried and researched the majority of method of measuring bodyfat. They all have some flaws.

Hydrostatic/Underwater Weighin is based on the dissection of 5 cadavers. None of those individuals was a normal healthy individuals.

The larger the number in a study, the greater the validity of the study.

The fewers the numbers in a study, the less validity the data has. Five cadavers is not enought to provide very reliable data.

Another problem, as I personally learned the hard way, is that unless you have you "Residual Lung Capacity" measured before being hydrostatically weighted, you bodyfat percentage reading Is worthless.

Providing the right protocol is followed with Hydrostatic, you can obtain a reasonable idea to you bodyfat percentage.

Ultrasound and the Futrex Near-Infrared Body Fat Analyzer reading are as inconsistent and flawed as the BIA. You noted how inaccurate infrared is. I've played with them, as well.

Calipers measurements are based off the research of Hydrostatic/Underwater Weighing. Thus, there is some inconsistency with them.

However, a great technician can give you a pretty good estimation (as Hydrostatic/Underwater Weighing does).

The problem is that there are very few personal trainers who are qualified to caliper clients.

How to know if you Personal Trainer is Qualified.

One indication that a personal trainer knows what they are doing is if they use a tape measure and pen. A great technican will measure specific sites with a tape measure and then mark the exact spot. They will usually take three readings at each site to insure they have obtained the correct numbers.

An incompetetent technician will grab the general area without measuring and caliper you.

Body Mass Index is the worse of all. Some individuals can be "Underweight" and "Overfat". That meaning their body weight is below normal but they have more fat than muscle.

An example of underweight an overfat is often senior citizens who weight in below normal but over the years they've lost muscle mass while adding bodyfat.

The opposite is also true, especially with athltes. An individual can be "Overweight" by chart measurments and "Underfat"...have a low percentage of body fat.

An extreme example of "Overweight" and "Underfat" are professional Bodybuilders who can be 6' tall/260 lbs and below 5% body fat.

My BMI is 29.5, with 30 being considered obese. I compete in an amateur sport I am "Overweight" by chart standards and "Normal Fat" by bodyfat percentage levels.

So, what a girl/guy to do?

Your two best and most economic tools are a tape measure and a mirror...or how you clothes fit.


Like most men, I put on bodyfat. My pants tell me quickly if I am adding or taking off bodyfat. The tape measure gives me a more definitive answer with a number.

Stipping down to your underwear in front of a mirror works or having a picture of yourself taken in shorts and a top. For those more self conscious, you can chose other clothing.

However, each time you have you picture taken, make sure you are standing the the same place withthe same clothes on.

Kenny Croxdale

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