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Weight and Body Fat
BMI – What Is It?
How does it work?
BMI stands for Body Mass Index, a statistical term derived from height and weight.
While body fat can be measured in many ways, the method used in your scale
It is closely linked to body fat and health outcomes. Over 50 organizations,
is bioelectrical impedance. This indirect method of determining body fat starts when
including the US Government and the World Health Organization, have adopted
a safe and very low electrical current is sent through the lower half of the body.
BMI guidelines. BMI is inversely related to fitness, meaning that the higher your
The electrical current flows more quickly through water and muscle than it will
BMI, the less likely you are to be fit. Every time your body analysis monitor reads
through bone and fat. The scale measures the speed of the current. Based on this
your weight and calculates your body fat, it also calculates your BMI. Along with
number, the scale estimates body fat using a multi-step, mathematical formula.
your weight and your body fat measurements, the BMI reading gives you yet one
more tool to monitor your health and fitness.
Is it accurate?
Measurements of body fat tend to fluctuate a lot more than simple weighing,
Body Water/Hydration Levels
and different methods of estimating body fat yield very different results. Just as
different scales give different results, different body fat analyzers can provide
General health standards indicate that one should consume approximately
very different body fat estimates. Even with the same scale the numbers will
64 oz of water per day from food and liquids to maintain a healthy level of hydra-
vary because:
tion. Maintaining a good hydration level will help improve your overall health and
• Weight loss tends to produce substantial, continuous, and unpredictable changes
general feeling of well-being. If your hydration levels are lower than average, you
in body water content. Because body fat analysis is determined by water content
should increase your water intake accordingly.
in the body, results can vary considerably from day to day.
• Hydration status affects body fat results. If you've just worked out, there is less
Body water/hydration level – how is it measured?
water for the electrical current to flow through. This may result in a higher body
The hydration level is measured by using Bioelectric Impedance Analysis (BIA).
fat result. In the same way, if you measure your body fat after drinking a lot of
The same analysis that is used to calculate your body fat is used to calculate your
fluid, it may appear that body fat is lower than it really is.
hydration level. Taking into consideration a user's age and gender, a calculation is
• Skin temperature can have an influence also. Measuring body fat in warm humid
made that determines the percentage of water.
weather when skin is moist will yield a different result than if skin is cold and dry.
Please note: It is not recommended to take the hydration measurements in
• As with weight, when your goal is to change body composition it is better to track
certain situations, such as following exercise, after drinking a glass of water, or
trends over time than to use individual daily results.
directly prior to, during or shortly after menstrual cycles. Hydration may not be at
• Results may not be accurate for persons under the age of 16, or persons with
normal levels during these times.
an elevated body temperature, diabetes or other health conditions.
Bone Mass – What Is It?
What you need to know!
• Percent body fat refers to the number of pounds of fat divided by your total body
Bone is a living, growing tissue. During youth, your body makes new bone tis-
weight and multiplied by 100.
sue faster than it breaks down older bone. In young adulthood, bone mass is at
• During weight loss, percent body fat doesn't appear to be reduced as quickly
its peak; after that, bone loss starts to outpace bone growth, and bone mass
as expected because total weight loss and total body fat are decreasing at the
decreases. But it's a long and very slow process that can be slowed down even
same time (for a more detailed explanation, see next section).
more through calcium-rich diets and weight-bearing exercise.
• Weight loss in the form of body fat and lean tissue (muscle) is common, and
is normal.
Who should monitor bone mass?
• To minimize the loss of lean tissue, include regular physical activity, especially
Most people have no need to monitor bone mass, but certain groups – post-
strength training, in your weight-loss plan.
menopausal women, men and women with certain diseases, and anyone who
takes medications that affect bone tissue – might want to watch for decreases in
Why do I lose weight but my body fat percentage doesn't change much?
bone mass. The bone mass reading is to be used as guide only. Watch for trends
Most body fat monitors show body fat as a percentage only. This body fat
over time and contact your healthcare provider for a more detailed explanation of
monitor shows you not only a percentage but the actual number of body fat
the readings and with any questions or concerns.
pounds (in fact, this is the measurement you see after your weight is displayed).
Why is that important? When you lose weight, both the numerator (pounds of
body fat) and denominator (total body weight) go down, so when it's calculated as
a body fat percentage, the number can be small. For example, 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
absolute number of body fat pounds lost. Remember, to minimize the loss of
lean tissue, include regular physical activity, especially strength training, in your
weight-loss plan.
Make the most of it!
Body Analysis Table
To summarize, make the most of the body analysis feature by:
• Tracking change over time and not day to day.
Always keep in mind that you know your body best. The following ranges of
• Using the same scale as much as possible.
body fat, BMI, body water and bone mass are offered as guides.
• Being extra-consistent in the time of day, day of the week, time before or after
food and fluid consumption, before or after exercise, etc., when measuring
too
lower
normal
higher
too
body composition.
low
than
than
high
normal
normal
While a scale/body fat monitor can be a useful tool on your weight-loss
journey, it's not in and of itself a program for losing weight. Studies show
BMI
<18.4
18.5-19.9
20-25
25.1-29.9
30+
that people lose three times more weight on Weight Watchers than they do
on their own.*
Body Fat
Come to a meeting and learn from us the best way to lose and maintain
weight. Call 1-800-651-6000 or go to WeightWatchers.com to find a
age
%
%
%
%
%
meeting near you.
Male
20-29
<13%
13.1-18%
18.1-23%
23.1-28% 28.1%+
30-39
<14
14.1-19
19.1-24
24.1-29
29.1+
Important Information Concerning
40-49
<15
15.1-20
20.1-25
25.1-30
30.1+
Weight Management
50-59
<16
16.1-21
21.1-26
26.1-31
31.1+
60-69
<17
17.1-22
22.1-27
27.1-32
32.1+
Your scale is the best tool for monitoring weight. While not the only measure
Female 20-29
<18
18.1-23
23.1-28
28.1-33
33.1+
of weight loss, scales are the most popular method used to gauge weight-loss
success. A scale measures the sum of your total body weight, which includes
30-39
<19
19.1-24
24.1-29
29.1-34
34.1+
bone, muscle, fat, and water.
40-49
<20
20.1-25
25.1-30
30.1-35
35.1+
50-59
<21
21.1-26
26.1-31
31.1-36
36.1+
Body weight fluctuates during the day, and from day to day,
60-69
<22
22.1-27
27.1-32
32.1-37
37.1+
depending on a variety of factors.
• Salt and carbohydrate intake can affect the body's water retention.
• A large meal adds weight and can cause water retention.
Body Water
• Dehydration from exercise, illness, or low fluid intake can result in weight loss.
age
%
%
%
%
%
• Muscle is also a factor. Heavy-duty resistance training can build muscle, which
can affect weight.
Male
20-69
<46.4%
46.5-49.9%
50-65%
65.1-70% 70.1%+
• The menstrual cycle can cause temporary weight gains and losses.
Female 20-69
<43.9
44-44.9
45-60
60.1-67.6
67.7+
When You're Losing Weight
Bone Mass
It's important not to put too much stock in the exact number on the scale,
age
%
%
%
%
%
because it can and will vary. This is especially true when you're dieting. Small
Male
20-29
<7.2%
7.3-7.5%
7.6-8.4%
8.5-8.7%
8.8%+
weight gains and losses are common as your body adjusts to fewer calories and
30-39
<7.0
7.1-7.3
7.4-8.2
8.3-8.5
8.6+
more exercise. Your scale is a valuable tool when used to track weight over a
period of weeks and months. Be aware that different scales often give different
40-49
<6.6
6.7-6.9
7-7.8
7.9-8.1
8.2+
results. The scale at your doctor's office may show one weight, and your scale at
50-59
<6.2
6.3-6.5
6.6-7.4
7.5-7.7
7.8+
home another. So don't get too caught up with a single number.
60-69
<5.9
6.0-6.2
6.3-7.1
7.2-7.4
7.5+
Female 20-29
<5.8%
5.9-6.1%
6.2-7%
7.1-7.3%
7.4%+
30-39
<5.6
5.7-5.9
6-6.8
6.9-7.1
7.2+
40-49
<5.2
5.3-5.5
5.6-6.4
6.5-6.7
6.8+
50-59
<4.8
4.9-5.1
5.2-6
6.1-6.3
6.4+
60-69
<4.5
4.6-4.8
4.9-5.7
5.8-6.0
6.1+
*Heshka S et al. Weight loss with self-help compared to a structured commercial program: a randomized controlled trial.
JAMA 2003; 289(14): 1792-1798.
Don't Overdo It!
Before Using Scale
A surefire way to get overly concerned with your weight is to weigh yourself too
Precautions for Use
often. We generally recommend weighing yourself no more than once a week
when you're dieting. Though it's hard to stick to this pattern, it's the best way to
CAUTION! Use of this device by persons with any electrical implant such
prevent unnecessary concern with normal weight fluctuations, which are unrelated
as a heart pacemaker, or by pregnant women, is not recommended.
1. Set switch on the base of the scale to measure in pounds (lb) or kilograms (kg).
to your weight-loss efforts. Regardless of your weighing habits, it's important that
you're consistent.
2. Set scale on floor. Surface must be level for accurate operation and safety.
Using the Weight Only Mode
Here are 5 rules for effectively monitoring your weight – weigh yourself:
• Once a week, on the same day of
• In the same place
Instructions for customizing your Weight Watchers Body Analysis and Weight
the week
• Wearing the same clothes
Tracker are below. However, the scale does not need to be programmed to operate
• At the same time of day
• Using the same scale
as a simple weigh scale.
1. Tap the scale with your foot to turn it on. The display will light up.
To keep track of your weight, record only one number for the week.
2. Wait until all digits light for several seconds and "0.0" appears.
This will give you a clear picture of any trend your weight is following.
When You're Maintaining Weight
Fluctuations in day-to-day weight tend to be smaller when weight is stable,
so a more frequent weigh-in pattern is helpful. To maintain a stable weight:
• Weigh yourself more often than once a week.
• Use the "5-pound rule" – research shows that people who keep weight
3. Step on the scale and stand still to measure your weight.
within a 5-pound range are more likely to maintain a healthy body weight
over the long term.
Facts You Should Know
Your Weight Watchers scale is a precise measuring instrument that is most
accurate when weighing a stationary object. To ensure accurate readings,
4. The weight reading stays lit for several seconds. Then the scale will shut
always try to stand on the same area of the scale platform and DO NOT MOVE.
off automatically.
Should the weight on the scale exceed the scale's capacity, you may see an error
message "ERR".
Electronic sensors are sensitive. Be careful not to drop or jar the scale.
Customizing Your Weight Tracker and
Place it gently onto floor surface, and store where it will be protected from impact.
Body Analysis Monitor
The scale is an electronic instrument and should never be submerged in water.
Clean with damp cloth and/or glass cleaner.
This tracking scale can be customized for up to 4 users. While the customization
In the event that the scale battery needs to be replaced, open the battery cover on
process is not difficult, it may be easiest to read all the instructions first to familiarize
the bottom of the scale and replace the old battery with a new 3V lithium battery.
yourself with them. Then keep the instruction manual handy as you go through the
process step by step.
Dispose of the old battery properly. Do not attempt to open the scale
or to remove any components. Servicing should be done by qualified
technicians only. See warranty information below.
Buttons: USER, SET, Up and Down arrows
To set your user data for weight tracking and body analysis:
1. Press SET. The whole display lights up.
2. Setting the user number
7. Start Weight: Your current weight appears on the
The whole screen stays lit for a few seconds, then "USER 1" displays. Press the
top of the screen. The scale will use your current weight
user button to change the user number: "USER 2 " flashes. Press up or down ar-
as the start weight; the bar corresponding to the start
rows to choose a different user number. Press SET to confirm.
weight on the left displays for 3 seconds.
8. Goal Weight: following established health guidelines,
the scale automatically calculates your goal weight as
10% off your start weight. The bar corresponding to the
goal weight on the left blinks.
• Press SET within 15 seconds to accept the goal weight.
3. Setting the height
Next, the height indicator "HT" and inch or cm symbol light up (if switch is set to
• Or press the up or down arrows to adjust the goal
lb, default is height in inches; if switch is set to KG, default is height in cm). Default
weight manually and then press the SET key within 15
height flashes (60 inches or 152 cm). Press the up or down arrows to adjust the
seconds once the desired goal weight is reached. Press
height. Pressing and holding either the up or the down arrow will advance numbers
SET to confirm.
quickly. Press SET to accept the height. Scale enters the age setting mode.
9. The scale will turn off automatically. It is now ready for use.
(LB version)
(KG version)
Daily Operation of the Scale
4. Setting the age
"AGE" appears and the default age 25 flashes. Press the
Once all your data has been set for the weight tracking and body analysis, you can
up or down arrows to adjust the age and press SET to
determine whether you want to go through the entire sequence of weight tracking
confirm. The scale enters the gender setting mode.
and then body analysis or choose one or the other individually. You can vary this
from day to day, every time you use the scale.
5. Setting the gender
• To go through the entire sequence, tap the scale to turn it on. When the display
The default female gender icon flashes. Press the up or
shows "0.0", press the USER button once (for user 1) or several times (for users 2,
down arrows to choose between male and female gender.
3 or 4) until you get to your user number. This is the default setting.
• To go through the weight tracking sequence only, do not tap the scale on but
press the USER button once (for user 1) or several times (for users 2, 3 or 4) until
6. Preparing the weight tracking data
you get to your user number.
• To go through the body analysis sequence only, tap the scale to turn it on, then
• Press USER to accept the gender and to continue the data
press the USER button once (for user 1) or several times (for users 2, 3 or 4) until
setting process for the weight tracking.
you get to your user number. The scale will recall the stored data (user number,
• "0.0" appears. Step on the scale to get your weight.
height, age and gender) for a few seconds. Press the DOWN button before scale
displays "0.0".
Note: If you press SET (instead of pressing USER) to
accept the gender, the scale will function as a body analysis
monitor for that user but will not track weight correctly. Scale will
run through the stored data for the user (height, age, gender) and then turn off
automatically. If you accidentally press SET, but want to use the scale both as
weight tracker as well as a body analysis monitor, simply go through the set-up
process again.
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