Thank you for your question and clarification!
While body fat scales are not the most accurate way to measure body
fat, they still provide a good guideline for the home user who
probably doesn't have access to other, more accurate (and more costly)
body fat testing methods like underwater weighing, DEXA body scanning,
and, heaven forbid, autopsy. The margin of error for body fat scales
is generally +/- 4%, while the so-called "gold standard" methods come
in at 1-3%. But while body fat scales can't quite compete with the big
boys of body fat measurement, many consider them to be superior to
methods like the low-tech caliper "pinch test," which relies heavily
on the skill of the user and can have an error margin as high as 8%.
Body fat scales work on the principle of conductivity. They send a
painless electrical signal through your feet; since the current moves
more quickly through muscle than through fat, the body fat scale uses
the speed at which the signal travels to determine your fat-to-muscle
There's a lot you can do to optimize your reading. I visited the
Tanita website (www.tanita.com) and reviewed the manual for the Tanita
"Duo" model body fat scale. Tanita recommends following these
guidelines to obtain the most accurate body fat readings:
- Place your scale on a hard, flat surface
- Measure yourself unclothed and with clean, dry feet
- Ensure your heels are correctly aligned with the electrodes
- Take your readings at least three hours after eating, sleeping or
hard exercise, and at the same time of day (Tanita suggests between 3
and 5 o'clock p.m. as an ideal time)
- Body fat scales are highly sensitive to the amount of water in your
body; take your measurements when you are neither under nor
- Ensure that your knees are not bent ? this interferes with the
movement of the electrical signal
Other factors that may affect your reading:
- The dehydrating effects of alcohol and caffeine consumption
- Certain medications
- Body temperature
- A very full bladder
- Severe calluses on heels or soles of feet
- Dirt on the electrodes (can be cleaned with rubbing alcohol)
- Wearing socks or nylons
- Menstruation/hormone fluctuations
Professional athletes and bodybuilders may have skewed readings due to
atypical hydration levels.
The verdict: While body fat scales might not hit the nail exactly on
the head, if used properly they're a good way to measure fluctuations
in body fat from your baseline measurement. If you can afford it, it
may be worthwhile to undergo hydrostatic weighing or DEXA scanning to
most accurately determine your baseline body fat percentage; after
that, you can use the Tanita scale to track fluctuations and progress.
You may be interested in the following resources:
Amazon.com user reviews of the Tanita Duo:
How to choose body fat monitors
Men's Health - Body Fat Scales
< http://www.menshealth.co.uk/talk/thread.phtml/post541915/ >
Tanita body fat scales: accurate or not?
< http://www.bodyresults.com/E2Tanitabodyfat.asp >
The Best Body Fat Scales And How To Make Them More Reliable
< http://www.sport-fitness-advisor.com/bodyfatscales.html >
The newest number ? body fat (Good Housekeeping magazine)
A comparison of 7 body fat scales; the Tanita model scores high on
durability but gets the lowest score for accuracy
Finally, keep in mind this sage advice from "Ways to Measure Body Fat"
at < http://dancingblonde.tripod.com/id87.html >:
"All of these are useful methods; but they should be taken as
indicators, and used to assess RELATIVE changes over several months.
Other ways to assess progress, of course, include how you feel in your
clothes (including body measurements), overall energy levels,
performance in your sport or activity of choice, and attainment of
your specific goals."
Here are some of the searches I used to find your answer:
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Please let me know if you require clarification ? all the best!