Who should not use this device
Bioelectrical Impedance Analysis impedance measurements should not be used by subjects with
the following characteristics:
(1) Electronic medical implants, e.g. cardiac pacemaker
A low level imperceptible electrical current will be sent through the body during
measurement, which may damage the implanted device or result in malfunction.
(2) Prosthetics and amputation
BIA measures impedance measured using an electric current sent through the body
through eight electrode contact points (two for each hand and two for each foot). As the
current cannot flow through prosthetic limbs, measurement is not possible.
(3) Pregnant Women
BIA equations are created based on statistical analysis of sample populations. If subject's
body composition differs significantly from these sample populations, equations derived
from "normal" healthy adults will be inherently less accurate in these subjects. Women
undergo a wide range of body composition changes during pregnancy, including but not
limited to change in fat percentage and body water. Without dedicated algorithms, pregnant
women should use results with caution and professional advice.
Measurement Rules
For best results, Body Composition Analysis should be conducted under specific controlled
conditions. Inconsistent measuring conditions will affect the accuracy and validity of BIA results,
and interpretation of body composition. The information below regarding the effect of various
factors on measurement results is largely sourced from related research by Kushner et al
1
.
Before measurement, please take note of the following:
3. Oshima Y & Shiga T. Within-day variability of whole-body and segmental bioelectrical impedance in a standing
position, European Journal of Clinical Nutrition 2006, 60, 938-941
The chart above depicts changes in segmental impedance throughout the day, as reported by
Oshima et al.
(NOTE: ZH-H, ZF-F, and ZH-F refer to Hand-to-Hand, Foot-to-Foot, and Hand-to-Foot
respectively.)
3
09:00
60
40
20
-20
-40
-60
0
12:00
15:00
18:00
(Ω)
impedance
Z
H-H
Z
F-F
Z
H-F
25
VI. INSTRUCTIONS FOR OPERATION
(1) Do not exercise or perform strenuous physical tasks before measurement.
Strenuous physical tasks and exercise can result in a temporary change in body
composition measurements. As BIA analyzes electrical impedance in the body, activities
that might affect impedance (e.g. increased perspiration, dehydration, blood circulation)
may affect measurement accuracy.
(2) Affect of food and drink on measurement results.
Ingestion of food and drink can affect impedance and weight, and thus analysis results.
This change generally lasts 2-5 hours after each meal. For most accurate results, BIA
measurements should be conducted in a fasting state (e.g. before breakfast)
2
Diuretics (e.g. caffeine, alcohol) can cause dehydration, creating an overestimation of body
fat. For most accurate results, diuretics should be avoided prior to measurement.
(3) Do not shower or bathe directly before measurement.
Perspiration can result in a temporary change in body composition measurements, as the
accuracy of BIA depends largely upon interpretation of measured impedance values, which
are affected greatly by hydration levels.
(4) Perform the measurement under normal temperature conditions (24-28°C)
Extreme temperatures (both hot and cold) can result in temporary physiological changes.
For example, excessive sweating due to heat can cause increased impedance
measurements, resulting in a higher fat calculation. For best results, measurements should
be conducted in an environment between 24-28°C.
(5) Remove shoes and socks before measurement.
Shoes and socks will interfere with the electric current, making measurement inaccurate or
in some cases, impossible.
(6) Avoid physical contact with other people during measurement.
Because BIA measures the impedance encountered as the electric current travels through
the subject's body, if another individual is touching the subject, the electric current may
pass through the other individual, causing inaccuracy in measurement results.
(7) Measure height accurately
Inaccurate height input will affect estimation of body composition.
(8) Perform the measurement in the morning.
As a general rule, BIA measurements should be performed in the morning to minimize the
influence of activity throughout the day on measurements.