Weight and Body Fat - How does it work?
While body fat can be measured in many ways, the method used in your scale is bioelec-
trical 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 dif-
ferent 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, it is better to track trends over time than to use individual daily results,
when your goal is to change body composition.
• 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 pounds 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?
Most body fat monitors show body fat as a percentage only. This body fat monitor shows
you not only a percentage but the actual number of body fat 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 tisse, include regular physical activity, especially strength training, in your
weight loss plan.
BMI
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 US
Government and the World Health Organization, have adopted BMI guidelines. BMI is
inversely related to fitness, meaning that the higher you BMI, the less likely you are to be
fit. Every time your body fat monitor reads your weight and calculates your body fat, it
also calculates your BMI. Along with you weight and your body fat measurements, the
BMI reading gives you yet one more tool to monitor your health and fitness.
General guidelines for BMI are as follows:
BMI less than 19: underweight
BMI 19-25: healthy weight
BMI 25-30: overweight
BMI over 30: obese
BMI Levels
In order to make your body fat and body water readings more accurate, your
monitor automatically calculates a BMI Level for you, based on the personal data you
have entered, as well as measurements the scale takes. Why is that important?People
with different BMIs have differences in muscle mass and body water levels. Do not be
alarmed if you do not see rapid changes to your category level: generally, your level
will change as you lose weight and become more fit. These changes happen gradually,
though, and you may not see them reflected for a few months of consistently following
a diet and exercise regimen.
Make the most of it!
To summarize, make the most of the body fat 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 fat
composition.
Always keep in mind that you know your body best. The following ranges
of Body Fat Percentages are offered as guides:
Healthy Range
of Body Fat
Age Females Males
Percentage Body Water/Hydration Levels:
According to the World Health Organization (WHO, 2001), the percentage of body water
should lie within the following ranges:
Women:
50-55%
Men:
60-65%
Children:
65-75%
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 that people
lose three times more weight on Weight Watchers than they do on their own.*
Age
Female
Males
18-39
21-32%
8-19%
40-59
23-33%
11-21%
60-79
24-35%
13-24%
Service Centre:
Conair Consumer Products Inc.
156 Parkshore Drive,
Brampton, Ontario.
L6T 5M1
Made in China
Consumer Call Centre E-mail:
1-800-472-7606
www.conaircanada.ca
*Heshka S, et al. Two-Year Randomized Controlled Study of Self-Help Weight Loss vs. A Structured Commercial Program.
The FASEB Journal 2001; 15(4):A623
©2006 Weight Watchers International Inc. All rights reserved. Weight Watchers is the registered trademark of
Weight Watchers International Inc. and used under license.
IB-7168
06CN1351
Scales by
Instructions
for use of
Weight Watchers
bathroom scale
Congratulations! By purchasing this Weight
Watchers Scale, you’ve made the first step
toward taking control of your weight. To get the
greatest benefit from your purchase, please read
this entire brochure before using your scale.
Model #WW73C
