2
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
The Tanita Body Fat Monitor/Scale TBF-604 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 fat in your body. 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 BIA method
The TBF-604 uses the BIA (Bioelectrical Impedance Analysis) technique. 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 in the muscle
and other body 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 meas-
uring the impedance. The signal used is very low, making it safe and imperceptible.
The illustration on the left show 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.
Advantages of the Tanita TBF-604
Previously, body fat percentage was determined by measuring the thickness of subcuta-
neous fat by pinching it with calipers, or by laying a person on a scanning bed and pass-
ing a current from hand to foot. However, these methods had problems; measurement
values varied, professional skills were required, and extensive time was required for
measurement. Currently, the standard methods of fat percentage measurement are
DEXA
(dual energy x-ray absorptiometry) and Hydrodensitometry (underwater weigh-
ing).
Based on data from both the DEXA and underwater weighing methods, Tanita established
a formula for estimating the percentage of body fat. There is a high correlation between
measurements taken with the TBF-604 and those obtained through DEXA and underwa-
ter weighing.
Principles of body fat percentage measurement
TANITA TBF-604 BODY FAT MONITOR/SCALE
20–39
40–59
60–79
Healthy
Overfat
Obese
Underfat
Healthy
Overfat
Obese
Underfat
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
Tanita’s patented “foot-pad” design sends a safe,
low-level electrical signal through the body to deter-
mine its composition.