Body Composition Scale – Measurement Techniques Part 5 (Types Of Anthropometric Measurement)

Skinfold methods

The skinfold estimation methods are based on a skinfold test, whereby a pinch of skin is precisely measured by calipers at several standardized points on the body to determine the subcutaneous fat layer thickness. These measurements are converted to an estimated body fat percentage by an equation. 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.

Height and circumference methods

There also exist formulas for estimating body fat percentage from an individual’s weight and girth measurements. For example, the U.S. 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 Navy the method is known as the “rope and choke.”

The U.S. Marine Corps and U.S. Army also rely on the Height and Circumference method. For males, they measure the neck and waist just above the navel. Females are measured around the hips, waist, and neck. These measurements are compared to a height/weight chart with age factored in as well. This method is used because it is a cheap and convenient way to implement a body fat test throughout the entire Department of Defense.

Due to different body compositions, those with larger necks may artificially generate lower body fat percentage calculations than those with smaller necks.

Body Composition Scale – Anthropometric methods

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. An excellent explanation of these methods is available in a PDF from the Academy For Educational Development.

Anthropometric Body Composition Methods Basis

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.

Anthropometric Body Composition Scales Measure Body Density Not Fat Percentage

Because most anthropomorphic formulas such as the Durnin-Womersley skinfold method, 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 tanks.

Sampling Issues Affect Accuracy of Anthropometric Body Fat Percentage Measurements

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.