Body Fat Testing

Body composition is defined as the relative percentage of body weight that is comprised of fat and fat-free tissue. There are multiple methods for testing the percentage of body fat including hydrostatic weighing, skinfold measurements, plethysmography, body mass index, and bioelectrical impedance analysis. A healthy range of body fat is 12-18% for males and 18-23% for females.

Techniques

Bioelectrical Impedance Analysis (BIA) This method of assessing body composition uses a small electrical current and measures the resistance or opposition to the current flow. This technique is based on the principle that resistance to electrical current is inversely related to the composition of wat within the body. The formula of height2/resistance is used for the general population while population-specific equations are also available. The standard error compares to the accuracy of skinfold measurements at approximately +/- 3%.

  BIA Protocol

• Stay adequately hydrated.

• Abstain from eating or drinking withn four hours prior to testing

• Abstain from vigorous physical activity within 12 hours pric

• Urinate within 30 minutes prior to testing

 • Avoid excessive water intake prior to testing

• Avoid alcohol consumption for 48 hours prior to testing

Densitometry

Hydrostatic Weighing: This method calculates the density of the body by immersing a person in water and measuring the amount of water that becomes displaced. The percentage of body fat is then determined by calculating the measured amount of water displaced in an equation based on Archimedes' principle. This method is the most widely used laboratory procedure to determine body density. Limitations of this method include the need to account for residual lung volume during submersion and evaluating patients that must tolerate water submersion during the testing. The standard error for this method is estimated at 2 to 2.5%.

Plethysmography: This method calculates the density of the body utilizing the amount of air displacement during testing within a specialized closed chamber. The change in pressure within the chamber is measured and converted to the percentage of body fat using a standardized equation.

Anthropometry

Skinfold Measurement: This method determines the overall per-centage of body fat through the measurement of nine standardized sites. The correlation relies on the theory that the amount of subcu-taneous fat is proportional to the total fat in the body. Limitations of this method include the requisite of an experienced examiner as well as variance from the standards based on gender, age, and ethnicity. Accuracy of measurement is within +/-3% with appropriate technique and equipment.

Skinfold Measurement Procedure

 • All measurements should be taken on the right side of the body

 • Take multiple measurements at each site to ensure accuracy and retest if the difference is greater than one to two millimeters

• Skinfold calipers should be positioned one centimeter away from the examiner's fingers when pinching the side, positioned perpendicular to the skinfold, and centered between the base and top of the fold

• Wait one to two seconds before reading the caliper

 • Maintain pinching of the site during the reading of the caliper

•There are seven and three site formulas to calculate the percentage body fat using particular sites, with additional specific formulas for gender, sport, ethnicity and age.