Body Fat Skinfold By Durnin And Womersley Calculator

How does the body fat skinfold by Durnin and Womersley calculator work?

This health tool estimates body fat percentage based on skinfold measurements from 4 sites. This is one of the most accurate skinfold methods, alongside the Jackson and Pollock formulas for 3, 4 or 7 sites.

According to the original study, the 4 site formula by Durnin and Womersley can be applied in the case of 16 to 72 year olds.

The method is said to have limited population specificity because it has been developed based on the study of a heterogenous group.

Before inputting data in the body fat skinfold calculator by Durnin and Womersley, measure the skinfold in milimeters in the 4 areas described below:

■ Biceps – Vertical fold on the anterior aspect of the arm, approximately 1 cm above the level of the triceps site.

■ Triceps – Vertical fold on the posterior midline of the upper arm, halfway between the bony processes (shoulder and elbow). The arm should be held freely to the side of the body.

■ Subscapular – Diagonal 45 degrees fold, 1-2 cm below the angle of the scapula.

■ Suprailiac – Diagonal fold, immediately superior and in line with the angle of the iliac crest, on the anterior axillary line.

In the original study the measurements have been taken on the right side of the body, however, no statistical difference has been observed between measurements on either sides.

In order to perform the calculations, the following steps are applied:

■ Computation of the logarithm of the sum of the four skinfolds in mm.

■ Determination of the body density in 10³ kg/m³ based on sum logarithm (L), subject gender and age group. The following table introduces the original Durnin and Womersley formulas:

The body density obtained is then converted to a body fat percentage amount using the Siri formula:

% Body Fat = (495 / Body Density) – 450

How to calculate body fat percentage?

Body composition can be defined in the case of the fitness field as the distribution of muscle and fat in the body. One of the most common used models is the 2 compartment one that divides the body weight in lean and fat weight. The latter is then expressed as percentage of the total body weight based on:

Body fat percentage (BF%) = (fat weight / total body weight) x 100

Body fat mass can also be obtained as a difference between subject weight and lean body mass. Beside the skinfold caliper measurement methods, BF% can be extracted from tape measurements in key areas of the body such as neck and waist circumference, based on the US Navy tape method.

Let’s take an example where the subject is a 30-year-old female, weighing 89 kg (196 lbs) and the following measurements have been taken with a caliper: Biceps = 18 mm; Triceps = 20 mm; Subscapular = 22 mm; Suprailiac = 32 mm.

■ The body density in this case is 1.02 x 10³ kg/m³;

■ The body fat percentage = 36.2%;

■ Given the 89 kg (196 lbs) weight and the BF%, the body fat mass = 32.2 kg;

■ The lean body mass = 56.8 kg.

The following table introduces fat level intervals based on gender, age group and fat percentage:

How to measure body fat with a skinfold caliper

There are several things to keep in mind when trying to perform a caliper test. There are different types of calipers available on the market, some that require a second person to measure, such as the known Harpenden skinfold caliper and others that are for self-use.

When conducting the measurements, the site localization needs to be accurate and a recommended average of three measurements for each site should be performed.

Some recommend the marking of the sites with a pen. Care is required when reading the caliper dial to the nearest 0.5 mm.

If the first two measurements vary by more than one millimeter, measurements should be taken until the variation between two is less than one millimeter. Measurements are then put in the formula to provide the body density and fat percentage.

Most of the criticism of the method revolves around the possible measurement inaccuracies and the fact that the method cannot reflect real fat distribution through the body and focuses on under skin deposits.

References

1) Durnin JV, Womersley J. (1974) Body fat assessed from total body density and its estimation from skinfold thickness: measurements on 481 men and women aged from 16 to 72 years. Br J Nutr. 1974 Jul;32(1):77-97.

2) Siri, W. E. (1961). Body composition from fluid space and density. In J. Brozek & A. Hanschel (Eds.), Techniques for measuring body composition (pp. 223-244). Washington, DC: National Academy of Science.

3) Peterson MJ, Czerwinski SA, Siervogel RM. (2003) Development and validation of skinfold-thickness prediction equations with a 4-compartment model 1,2,3. Am J Clin Nutr. vol. 77 no. 5 1186-1191.

4) Vasudev S, Mohan A, Mohan D, Farooq S, Raj D, Mohan V. (2004) Validation of body fat measurement by skinfolds and two bioelectric impedance methods with DEXA--the Chennai Urban Rural Epidemiology Study [CURES-3]. J Assoc Physicians India; 52:877-81.