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Principles of Estimating Body Fat Percentage
The UltimateScale allows you to estimate your body fat percentage at home
as easily as you measure your weight.
What is Body Fat Percentage?
Body fat percentage is the percentage of your body that is fat. Until now, your absolute
weight has determined whether or not you were considered overweight or 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.
The chart below shows four ranges of body fat percentage.
The BIA Method
Tanita’s UltimateScale uses the BIA (Bioelectrical Impedance Analysis) method. In this
method, a safe, low-level electrical signal is passed through the body. It is difficult for the
signal to flow through fat in the human body, but easy to flow through moisture found in
muscle and other lean tissues. The difficulty with which a signal flows through a substance
is called impedance. So the amount of fat in the body can be accurately estimated by
measuring the impedance. The signal used is very low, making it safe and imperceptible.
The illustration on the left shows how the signal travels through the body.
Body Fat Percentage Fluctuations in a Day
Hydration levels in the body may affect body fat readings. Readings are usually highest in the
early waking hours, since the body tends to be dehydrated after a long night’s sleep. For the
most accurate reading, a person should take a body fat percentage reading at a consistent
time of day under consistent conditions.
Besides this basic cycle of fluctuations in the daily body fat readings, variations may be
caused by hydration changes in the body due to eating, drinking, menstruation, illness,
exercising, and bathing. Daily body fat readings are unique to each person, and depend upon
one’s lifestyle, job and activities.
The graph on the left shows an example of daily body fat percentage fluctuations.
Tanita’s patented “foot-pad” design sends a safe,
low-level electrical signal through the body to deter-
mine its composition.
6 am
22
21
20
19
18
17
10 am 2 pm 6 pm 10 pm Time
Body Fat %
Daily fluctuations in body fat percentage based
on the BIA method.
20–39
40–59
60–79
Healthy Overfat ObeseUnderfat
Healthy Overfat ObeseUnderfat
Based on NIH/WHO BMI Guidelines.
As reported by Gallagher, et al., at NY Obesity Research Center.
To determine the percentage of body fat that is appropriate for your body, consult your physician.
10%0% 20% 30% 40%
20–39
40–59
60–79
Female
Body Fat Ranges for Standard Adults
Age
Male
Age
1., 2.
1.
2.
Additional Information
Further information on body fat is available at our
Web site, www.tanita.com and in our educational
brochures—call 1-800-TANITA-8 to request a
brochure (USA and Canada only).