Body fat can be measured in several different ways:

Here is how I do it:

Body Fat Monitoring bathroom scale.  Model TBF-531 by Tanita (TM)

Body Fat Monitor (HBF-306) by Omron (TM)

I use the TBF-531 Body Fat Monitor/Scale by Tanita.  (Note: This model is no longer manufactured, but they have newer models that do the same thing)

I also use the Omron Fat Loss Monitor HBF-306.  Both devices use the electrical impedance method of measurement. I take two measurements, one from each device and then average the two numbers.

The user manual for the Tanita is much larger than the Omron so I’m going to use that manual as a basis of discussion for the rest of this blog post.  In comparing the Tanita user manual to other information I’ve read I’ve concluded that the information from the manual is basically accurate.   It is, of course, written in such a way as to make their product sound great and awesome and the best scale created since the building of the pyramids, but hey they have to make a living too. 😉

Excerpt from the TBF-531 Owner’s manual

The chart shows the reasonable ranges of body fat percentage

Body fat percentage is the percentage of fat in your body.  Until now, your absolute weight has determined whether or not you were considered obese.  In recent years, the definition of obesity has been refined to mean the presence of excess body fat.   too much body fat has been linked to conditions such as high blood pressure, heart disease, diabetes, cancer, and other disabling conditions.

Comment from little ole me:  The figures in this chart while given in a very broad range, are fairly accurate.  I’ll do a later post that talks about “What is a healthy body fat percentage?”

Body fat percentage measurement (From the Tanita Manual)

The TBF-531 uses the BIA (Bioelectrical Impedance Analysis) technique.  In this method, a low-frequency electrical current is passed through the body.  It is difficult for a current to flow through fat in the human body, but easy to flow through moisture in the muscle.  The current used for measurement is very low, making it safe and imperceptible.

Comment from little ole me: There are lots of warnings all over the box and in the owner’s manual that folks with pacemakers, children 7 yrs or younger, adults 70 yrs or older, pregnant women, persons undergoing dialysis, persons suffering from edema should not use the device. Their lawyers probably wrote those warnings so they wouldn’t get sued but hey, why take the chance.  If you fit one of those categories, you might want to rethink using BIA.

Body fat percentage fluctuations in a day (From the Tanita Manual)

For the most accurate reading, a person should measure body fat percentage in the evening before sleeping because electrical resistance usually increases during sleep and decreases when the body is active.  While readings taken at other times of the day may not have the same absolute value, they are accurate for determining the percentage of change as long as the readings are done at a consistent time every day.
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Besides this basic cycle of fluctuations in the daily body fat percentage, variations may be caused by changes of moisture content in the body due to eating, drinking, menstruation, urination, illness, exercising, and bathing.  Daily body fat percent fluctuation is unique for each person, and depends upon their electrical resistance cycle, life style, job and activities.

Comment from little ole me: Basically what they are saying is:  You have to be consistent.   The measurement is dependant on a lot of things which affect the electrical flow, specifically the level of moisture in your body.  If you are dehydrated, you’ll get a different result.  If you just finished exercising.  If you are under a lot of stress, then that affects it.  If you just stepped out of the shower and are still damp, that will  affect it.   So… now you see why I’m using  the averages of the two daily measurements and a weekly average as well.

Advantages of the Tanita TBF-531

Comment from little ole me: I’ll spare you the advertising blurb about how good their product is.   Let me summarize instead.  Of all the methods I’ve listed here, BIA will probably work best for most folks because it is easy, inexpensive and if used consistently can provide a good relative measurement.

The BIG (pardon the pun) advantage of a home scale like this one is Uhmm.  Duh, It is in your home!  Even if the results are subject to a wide range of environmental factors and the testing method is the sometimes inaccurate, the advantage of being able to conduct the test in your home on a daily basis outweighs (again, pardon the pun) these disadvantages.

It also has the advantage of being PRIVATE; no ex-marine sumo-gym-teacher type is going to look upon my vast acres of blubber and make me pay for the privilege of having him pinch me or dunk me then tell me that I’m out of shape and overweight.  This I know already.  So, I take my own measurements in the privacy of my bathroom where no one can see my naked body and run screaming (or have to schedule a session with their therapist) and use those measurements as a relative measurement not as an absolute one.

See ya on the dance floor!