BMI — What Is It?
BMI stands for Body Mass Index, a statistical term derived from height and weight.
It is closely linked to body fat and health outcomes. Over 50 organizations,
including the Australian and New Zealand Goverments and the World Health
Organization, have adopted BMI guidelines. BMI is inversely related to fitness,
meaning that the higher your BMI, the less likely you are to be fit. Every time your
body analysis monitor reads your weight and calculates your body fat, it also cal-
culates your BMI. Along with your weight and your body fat measurements, the
BMI reading gives you yet one more tool to monitor your health and fitness.
Body Water/Hydration Levels
General health standards indicate that one should consume approximately
2L of water per day from food and liquids to maintain a healthy level of
hydration. Maintaining a good hydration level will help improve your overall health
and general feeling of well-being. If your hydration levels are lower than average,
you should increase your water intake accordingly.
Body water/hydration level – how is it measured?
The hydration level is measured by using Bioelectric Impedance Analysis (BIA).
The same analysis that is used to calculate your body fat is used to calculate your
hydration level. Taking into consideration a user’s age and gender, a calculation is
made that determines the percentage of water.
Please note: It is not recommended to take the hydration measurements in
certain situations, such as following exercise, after drinking a glass of water, or
directly prior to, during or shortly after menstrual cycles. Hydration may not be
at normal levels during these times.
Bone Mass — What Is It?
Bone is a living, growing tissue. During youth, your body makes new bone
tissue faster than it breaks down older bone. In young adulthood, bone mass is
at its peak; after that, bone loss starts to outpace bone growth, and bone mass
decreases. But it’s a long and very slow process that can be slowed down even
more through calcium-rich diets and weight-bearing exercise.
Who should monitor bone mass?
Most people have no need to monitor bone mass, but certain groups – post-
menopausal women, men and women with certain diseases, and anyone who
takes medications that affect bone tissue – might want to watch for decreases in
bone mass. The bone mass reading is to be used as guide only. Watch for trends
over time and contact your healthcare provider for a more detailed explanation of
the readings and with any questions or concerns.
Muscle Mass — What Is It?
Muscle mass is part of your lean body mass and gets measured as a percentage
of your total body weight. There are different types of muscles in the body and
men and women tend to have different amounts of muscle tissue. If you are losing
weight, it is important to check if you are losing fat or muscle weight. Typically,
you would want to lose fat rather than muscle. Muscles give tone and shape to
your body and they help burn energy, even at rest. To minimize the loss of lean
tissue, include regular physical activity, especially strength training, in your weight-
loss plan.
Weight and Body Fat
How does it work?
While body fat can be measured in many ways, the method used in your scale
is bioelectrical impedance. This indirect method of determining body fat starts when
a safe and very low electrical current is sent through the lower half of the body.
The electrical current flows more quickly through water and muscle than it 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, mathematical formula.
Is it accurate?
Measurements of body fat tend to fluctuate a lot more than simple weighing,
and different methods of estimating body fat yield very different results. Just as
different scales give different results, different body fat analyzers can provide
very different body fat estimates. Even with the same scale the numbers will
vary because:
• Weight loss tends to produce substantial, continuous, and unpredictable changes
in body water content. Because body fat analysis is determined by water content
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
water for the electrical current to flow through. This may result in a higher body
fat result. In the same way, if you measure your body fat after drinking a lot of
fluid, it may appear that body fat is lower than it really is.
• Skin temperature can have an influence also. Measuring body fat in warm, humid
weather when skin is moist will yield a different result than if skin is cold 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 results.
• Results may not be accurate for persons under the age of 16, or persons with
an elevated body temperature, diabetes or other health conditions.
What you need to know!
• Percent body fat refers to the number of kilograms of fat divided by your total
body weight and multiplied by 100.
• During weight loss, percent body fat doesn’t appear to be reduced as quickly
as expected because total weight loss and total 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, include regular physical activity, especially
strength training, in your weight-loss plan.
Why do I lose weight but my body fat percentage doesn’t change much?
Remember that your Weight Watchers body fat monitor is showing your body fat as
a percentage, not as an absolute number of kilograms. At the beginning of a weight
loss program, a person may weigh 100kg and show 30% body fat, equaling 30kg of
fat (30% of 100 kg = 30kg). A few weeks later, the same person may have lost a
substantial amount of weight. Weight is now at 90kgs, yet body fat is still at 30%.
Why? Did that person not lose any fat? Yes, they did. At 90kgs with 30% body fat,
the person now has 27kgs of body fat (30% of 90kgs = 27kgs), meaning that 3kgs
of the total 10kgs lost were fat. So, do not be overly concerned if your percentage
of body fat does not change despite the fact that you are losing weight.
Remember, to minimise the loss of lean tissue include regular physical activity,
especially strength training, in your weight loss plan.
weight gains and losses are common as your body adjusts to fewer calories and
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
results. The scale at your doctor’s office may show one weight, and your scale at
home another. So don’t get too caught up with a single number.
Don’t Overdo It!
A surefire way to get overly concerned with your weight is to weigh yourself too
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
prevent unnecessary concern with normal weight fluctuations, which are unrelated
to your weight-loss efforts. Regardless of your weighing habits, it’s important that
you’re consistent.
Here are 5 rules for effectively monitoring your weight – weigh yourself:
To keep track of your weight, record only one number for the week.
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.
• Research shows that people who keep weight within a 2-3kg 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,
always try to stand on the same area of the scale platform and DO NOT MOVE.
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.
Place it gently onto floor surface, and store where it will be protected from impact.
The scale is an electronic instrument and should never be submerged in water.
Clean with damp cloth and/or glass cleaner.
In the event that the scale batteries need to be replaced (display shows “Lo”),
remove the screw from the battery cover on the bottom of the scale and remove
the cover. Replace the old batteries with 3 new AAA alkaline batteries. Clean the
battery contacts and also those of the device prior to battery installation. Ensure
the batteries are installed correctly with regard to polarity (with the side facing “+”
up), then replace the battery cover and tighten the screw. Remove batteries from
equipment that is not to be used for an extended period of time. Remove used
batteries promptly. Dispose of the old batteries properly. Do not attempt to
open the scale or to remove any components. Servicing should be done by
qualified technicians only. See warranty information provided.
• Once a week, on the same day of
the week
• At the same time of day
• In the same place
• Wearing the same clothes
• Using the same scale
Before Using Scale
Precautions for Use
CAUTION! Use of this device by persons with any electrical implant such
as a heart pacemaker, or by pregnant women, is not recommended.
Please consult your physician should you have any questions about the use
of this product in relation to any condition you may have, or treatment you
may be receiving.
1. Remove all packaging materials.
2. Remove the isolator tab from the battery compartment – without opening the
battery cover at the bottom of the scale, gently pull out the isolator tab. In case the
tab cannot be pulled out, if it does not completely pull out or if the display does not
light up when you tap the scale, remove the screw from the battery cover, remove
the cover and gently pull out the isolator tab. Ensure the batteries are installed
correctly and then replace the battery cover and tighten the screw.
3. For best accuracy, place scale on tile or hardwood floor, rather than uneven,
flexible or soft flooring (such as carpet).
Using the Weight Only Mode
Instructions for customizing your Weight Watchers Body Analysis Scale are
provided. However, the scale does not need to be programmed to operate as a
simple weight scale.
1. Tap the scale with your foot to turn it on. The display will light up.
2. Wait until all digits light for several seconds and “0.00” appears.
3. Step on the scale and stand still to measure your weight. The display will blink
and then shows your weight.
4. The weight reading stays lit for several seconds. Then the scale will shut
off automatically.
5. When scale display is on, set switch on the base of the scale for measuring in
pounds (lb) or kilograms (kg).
Body Analysis Table
Always keep in mind that you know your body best. The following ranges of body
fat, BMI, body water, bone mass and muscle mass are offered as guides.
Make the most of it!
To summarize, make the most of the body analysis feature by:
• Tracking change over time and not day to day.
• Using the same scale as much as possible.
• 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
body composition.
While a scale can be a useful tool on your weight loss journey,
it’s not a complete program for losing weight.
Come to a Weight Watchers meeting or join online to learn the best
way to lose and maintain weight. In Australia: 13 19 97 or
www.weightwatchers.com/au, in New Zealand: 0800 009 009 or
www.weightwatchers.co/nz.
Important Information Concerning
Weight Management
Your scale is the best tool for monitoring weight. While not the only measure
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
bone, muscle, fat, and water.
Body weight fluctuates during the day, and from day to day,
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.
• Dehydration from exercise, illness, or low fluid intake can result in weight loss.
• Muscle is also a factor. Heavy-duty resistance training can build muscle,
which can affect weight.
• The menstrual cycle can cause temporary weight gains and losses.
When You’re Losing Weight
It’s important not to put too much stock in the exact number on the scale,
because it can and will vary. This is especially true when you’re dieting. Small
too lower normal higher too
low than than high
normal normal
BMI <20 20-25 25+
Body Fat
age % % % % %
20-29 <13% 13.1-18% 18.1-23% 23.1-28% 28.1%+ Male
30-39 <14 14.1-19 19.1-24 24.1-29 29.1+
40-49 <15 15.1-20 20.1-25 25.1-30 30.1+
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+
Female 20-29 <18 18.1-23 23.1-28 28.1-33 33.1+
30-39 <19 19.1-24 24.1-29 29.1-34 34.1+
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+
60-69 <22 22.1-27 27.1-32 32.1-37 37.1+
Body Water
age % % % % %
Male 20-69 <46.4% 46.5-49.9% 50-65% 65.1-70% 70.1%+
Female 20-69 <43.9 44-44.9 45-60 60.1-67.6 67.7+
Bone Mass
age % % %
Male 20-29 <7.6% 7.6-8.4% 8.5%+
30-39 <7.4 7.4-8.2 8.3+
40-49 <7.0 7-7.8 7.9+
50-59 <6.6 6.6-7.4 7.5+
60-69 <6.3 6.3-7.1 7.2+
Female 20-29 <6.2% 6.2-7% 7.1%+
30-39 <6.0 6-6.8 6.9+
40-49 <5.6 5.6-6.4 6.5+
50-59 <5.2 5.2-6 6.1+
60-69 <4.9 4.9-5.7 5.8+
Muscle Mass
age % % %
20-29 <33% 44.1% - 55% 66.1% + Male
30-39 <32% 42.4% - 52.7% 63.1% +
40-49 <31% 40.4% - 49.7% 59% +
50-59 <30% 38.8% - 47.3% 56% +
60-69 <29% 37.8% - 46.3% 55% +
Female 20-29 < 26% 31.8% - 37.3% 43% +
30-39 < 25% 30.1% - 35% 40% +
40-49 < 23% 28.1% - 33% 38% +
50-59 < 22% 26.8% - 31.3% 36% +
60-69 < 21% 25.8% - 30.3% 35% +
