Weight and Body Fat
How
does it
work?
While body
fat
can be
measured
in
many ways, the method used in your sca
l
e
is bioelectrical impedance. This
i
ndirect
method
of determining body fat starts when
a safe and very low electrica
l
current
i
s
sent through the lower half of the body.
The electrical current flows more quickly
through
water and muscie than
i
t
will
through
bone and fat. The scale measures the speed of the current. Based on this
number
,
the scale estimates body fat
using
a mUlti-step, mathematica
l
fo
rmula
.
Is
it
accurate?
Measurements
of body
fat
te
nd
to
fluctuate
a
lot
more than
simple
weigh
i
ng,
and different methods of est
i
mating body fat yield very different results
.
Just as
different scales give different resulls,
d
ifferent
body
fat analyzers can provide
very
differen
t
body
fat
estimates. Even with the same scale
the
numbers wil
l
vary because:
• Weight
l
oss
tends
to produce substantial, cont
i
nuous, and unpredictable changes
in
body wate
r
content. Because
body
fat analysis is determ
i
ned by water content
in the body, results can vary considerab
l
y
fr
om day to day
.
•
Hydration
status
affects body
fat
results. If you've
Just
worked out,
there is less
water for the e
l
ectrical current
to
flow
through. This may resul
t
in a
higher
body
fat result.
In
the same way,
I
f you measure your body
fat
after drinking a
lot
of
flu
i
d,
i
t
may appear that body
fat
I
s lower
than
it
'
real
l
y is.
•
Sk
i
n temperature
can
have an
i
nfluence a
l
so. Measur
i
ng body fat in warm humid
weather when skin
is
mois
t
w
i
ll yield a different resu
l
t than
if
skin
is
co
l
d and dry
.
•
As with weight, when your goal
is
to change body composition it is better
to
track
trends over time
than
to use individual daily
resu
l
ts.
• Results may not be accurate for persons
under
the age of 16, or persons with
an elevated body temperature, diabetes or other hea
lt
h cond
i
t
i
ons.
What
you
need
to
know!
•
Percent body fat refers to
the
number of pounds of fat divided by your
total
body
weight and multipl
i
ed by
100.
• During weight loss, percent body fat doesn't appear
to
be reduced as quickly
as expec
t
ed
because
total weight
loss
and
t
otal body fat are
decreasing
at the
same
time
(for a more detailed explanation, see
next
section).
•
Weight
loss in
the
form
of body fat and
lean
tissue (muscle)
is
common, and
is
normal.
•
To minimize
the
loss
of lean
tissue,
in
clude regu
l
ar physical activ
i
ty, especially
s
t
rength training,
in
your weigh
t
-loss
plan.
Why do I
lose weight but my body fat
percentage
doesn't
change much?
Most body fat monitors show body
f
a
t
as a
percentage
only. This body fat
mon
i
tor shows you not on
l
y a percen
t
age
but the
actual
number
of body
fat
pounds (in fact, this
is
the measurement you see after your weight
is
displayed).
Why
is that
im
portant? When you lose weight
,
both
the
numerator (pounds of
body
fat) and denominator (total
body
weight) go down, so when
it's
calcu
l
ated as
a body
fat
percentage,
the
number can be smal
l.
For examp
l
e, a person may weigh
200 pounds and have 40% body
fat
80 pounds of
body
fat)
.
He/She loses
20 pounds, but the body fat has only
dropped
4% to 36%. That 4% of body
fat
was
16
pounds
of fat
a very
significant
amount! So do not be overly concerned if you
do
not
see
the
percentage change quickly as you are
losing
weight: monitor the
abso
l
ute number of body fat pounds lost. Remember, to minimize the loss of
l
ean t
i
ssue, include regular physical activ
i
ty
,
especially strength training
,
in your
weight
-l
oss
plan
.
