There are a number of ways to estimate what percentage of your weight
is fat. But measuring body fat is not done routinely, because all of these methods
have advantages and disadvantages as well as margins of error.
Some common methods
Skinfold thickness. An instrument called a caliper is used to measure the thickness of
fat at one or more sites on the body. Measuring skin-fold thickness gives a reasonable
estimate of body fat composition, especially if measurements are taken from several
sites. But the results can vary when different people take the measurements or if
the person taking the measurements is not well-trained.
A small electrical current is passed through your body, allowing the electrical resistance
of your body to be measured. Bioelectrical impedance measurement of body fat is based
on the principle that lean body mass conducts electricity better than fat body mass.
Along with the electrical resistance, your height and weight are used to calculate
your percent of body fat. There are some devices, including body fat scales, that
you can buy to calculate your percentage of body fat using this method. Results can
vary based on how much water is in your body and where the electrodes are placed.
weighing. This is also called hydrodensitometry. The difference between your weight
in and out of the water is used to calculate your body density. Your body fat percentage
is estimated based on the principle that fat tissue is less dense than muscle and
DXA, or dual-energy X-ray absorptiometry. This is a type of X-ray
that can tell how much fat tissue you have and where it is.
plethysmography. This is similar to underwater weighing except it uses air instead
of water. The difference between the air pressure inside a sealed chamber when you
are in it and when you are out of it is used to calculate your body density. This
number (your body density) and your weight when out of the chamber are used to estimate
your body fat percentage.
Experts differ in their opinions about what
is a healthy percentage of body fat. In general, 10% to 22% body fat is considered
healthy in an adult man, and 20% to 32% body fat is considered healthy in an adult
woman. Above or below this level is usually considered unhealthy and could put you
at risk for health problems.
Percentage of body fat will vary between different
population groups. Your age, sex, and activity level will also affect your percentage
of body fat. For example, endurance runners have less body fat than swimmers. People
living near the North or South Pole generally have more body fat than people living
in more moderate temperature zones.
Remember that percentage of body fat, by
itself, doesn't tell whether a person is healthy or unhealthy. The location of the fat is also important. Body
fat around your stomach can put you at risk for more health problems than if your
fat is around your hips, buttocks, and thighs instead.
Staff Primary Medical ReviewerAnne
C. Poinier, MD - Internal Medicine Kathleen Romito,
MD - Family Medicine Martin J. Gabica, MD - Family
Medicine Specialist Medical ReviewerRhonda O'Brien, MS, RD, CDE - Certified Diabetes Educator
This information does not replace the advice of a doctor.
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