Body density measurement -
The two methods may give different percentages, without being inconsistent, as they measure fat in different parts of the body. More sophisticated instruments for domestic use are available with electrodes for both feet and hands.
There is little scope for technician error as such, but factors such as eating, drinking and exercising must be controlled [16] since hydration level is an important source of error in determining the flow of the electric current to estimate body fat.
The instructions for use of instruments typically recommended not making measurements soon after drinking or eating or exercising, or when dehydrated.
Instruments require details such as sex and age to be entered, and use formulae taking these into account; for example, men and women store fat differently around the abdomen and thigh region. Different BIA analysers may vary. Population-specific equations are available for some instruments, which are only reliable for specific ethnic groups, populations, and conditions.
Population-specific equations may not be appropriate for individuals outside of specific groups. There exist various anthropometric methods for estimating body fat. The term anthropometric refers to measurements made of various parameters of the human body, such as circumferences of various body parts or thicknesses of skinfolds.
Most of these methods are based on a statistical model. Some measurements are selected, and are applied to a population sample. For each individual in the sample, the method's measurements are recorded, and that individual's body density is also recorded, being determined by, for instance, under-water weighing, in combination with a multi-compartment body density model.
From this data, a formula relating the body measurements to density is developed. Because most anthropometric formulas such as the Durnin-Womersley skinfold method, [18] the Jackson-Pollock skinfold method, and the US Navy circumference method, actually estimate body density, not body fat percentage, the body fat percentage is obtained by applying a second formula, such as the Siri or Brozek described in the above section on density.
Consequently, the body fat percentage calculated from skin folds or other anthropometric methods carries the cumulative error from the application of two separate statistical models. These methods are therefore inferior to a direct measurement of body density and the application of just one formula to estimate body fat percentage.
One way to regard these methods is that they trade accuracy for convenience, since it is much more convenient to take a few body measurements than to submerge individuals in water.
The chief problem with all statistically derived formulas is that in order to be widely applicable, they must be based on a broad sample of individuals. Yet, that breadth makes them inherently inaccurate. The ideal statistical estimation method for an individual is based on a sample of similar individuals.
For instance, a skinfold based body density formula developed from a sample of male collegiate rowers is likely to be much more accurate for estimating the body density of a male collegiate rower than a method developed using a sample of the general population, because the sample is narrowed down by age, sex, physical fitness level, type of sport, and lifestyle factors.
On the other hand, such a formula is unsuitable for general use. The skinfold estimation methods are based on a skinfold test , also known as a pinch test , whereby a pinch of skin is precisely measured by calipers , also known as a plicometer , [19] at several standardized points on the body to determine the subcutaneous fat layer thickness.
Some formulas require as few as three measurements, others as many as seven. The accuracy of these estimates is more dependent on a person's unique body fat distribution than on the number of sites measured.
As well, it is of utmost importance to test in a precise location with a fixed pressure. Although it may not give an accurate reading of real body fat percentage, it is a reliable measure of body composition change over a period of time, provided the test is carried out by the same person with the same technique.
Skinfold-based body fat estimation is sensitive to the type of caliper used, and technique. This method also only measures one type of fat: subcutaneous adipose tissue fat under the skin. Two individuals might have nearly identical measurements at all of the skin fold sites, yet differ greatly in their body fat levels due to differences in other body fat deposits such as visceral adipose tissue: fat in the abdominal cavity.
Some models partially address this problem by including age as a variable in the statistics and the resulting formula. Older individuals are found to have a lower body density for the same skinfold measurements , which is assumed to signify a higher body fat percentage.
However, older, highly athletic individuals might not fit this assumption, causing the formulas to underestimate their body density.
Ultrasound is used extensively to measure tissue structure and has proven to be an accurate technique to measure subcutaneous fat thickness. By making thickness measurements at multiple sites on the body you can calculate the estimated body fat percentage.
Ultrasound equipment is expensive, and not cost-effective solely for body fat measurement, but where equipment is available, as in hospitals, the extra cost for the capability to measure body fat is minimal. There also exist formulas for estimating body fat percentage from an individual's weight and girth measurements.
For example, the U. Navy circumference method compares abdomen or waist and hips measurements to neck measurement and height and other sites claim to estimate one's body fat percentage by a conversion from the body mass index.
In the U. Navy, the method is known as the "rope and choke. The U. Army and U. Marine Corps also rely on the height and circumference method.
Females are measured around the hips, waist, and neck. These measurements are then looked up in published tables, with the individual's height as an additional parameter.
This method is used because it is a cheap and convenient way to implement a body fat test throughout an entire service. Methods using circumference have little acceptance outside the Department of Defense due to their negative reputation in comparison to other methods.
The method's accuracy becomes an issue when comparing people with different body compositions, those with larger necks artificially generate lower body fat percentage calculations than those with smaller necks. Body fat can be estimated from body mass index BMI , a person's mass in kilograms divided by the square of the height in meters; if weight is measured in pounds and height in inches, the result can be converted to BMI by multiplying by These formulae are based on work by researchers published in peer-reviewed journals, but their correlation with body fat are only estimates; body fat cannot be deduced accurately from BMI.
Body fat may be estimated from the body mass index by formulae derived by Deurenberg and co-workers. Internal and external cross-validation of the prediction formulas showed that they gave valid estimates of body fat in males and females at all ages.
However — contrary to the aforementioned internal and external cross-validation —, these formulae definitely proved unusable at least for adults and are presented here illustratively only. Still, the following formula designed for adults proved to be much more accurate at least for adults: [28].
Other indices may be used; the body adiposity index was said by its developers to give a direct estimate of body fat percentage, but statistical studies found this not to be so. Contents move to sidebar hide.
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doi : PMID Mayo Clinic Proceedings. November 1, The American Journal of Sports Medicine. S2CID Retrieved July 29, The Complete Guide to Sports Nutrition 6th ed. See more equations for measuring body fat using skinfold measures.
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Skinfold measurement equations can help produce densitty relatively accurate estimate Body density measurement body fat as long as the desity are taken densityy. Two equations demsity required Non-toxic personal care products this process -- one to estimate body measurekent and one Creams for cellulite reduction estimate percent body wakefulness and brain function from the body density. Professionals use measurementt Body density measurement of wakefulness and brain function equations depending on how many skinfold sites are taken and the gender, age and ethnicity of the person being measured. Women typically have more body fat than men and often carry it in different locations. Because of this, there are different skinfold sites for men and women along with different equations for each gender. For example, a three-site formula developed by Andrew Jackson and M. Pollock for women involves calculating body density using the sum of measurements taken at the triceps, thigh and suprailium, but the corresponding formula for men uses skinfold sites at the abdomen, chest and thigh.
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