What are the Methods of Anthropometric Measurements and Body Composition?

With the recent interest in personal health, nutritional status and fitness, several methods of estimating body fat have been developed and used in clinical setting. The accurate measurement of Learn Body Mass is now the most rational basis for nutritional and exercise prescriptions.

The importance of clinical body composition is now being recognized. There is evidence that research and interest in body composition was explored centuries ago by Archimedes, though most of the research data that is available on human body composition has been completed in the last forty years. Various body composition analysis techniques are:

Body-Mass Index

It has recently been used to quantify an individual’s obesity level. BMI is derived from a ratio equation of height squared divided by weight. Here again, only an individual’s height and weight are used can no indication of actual lean or fat mass can be determined. Thus, BMI offers little advantage over the existing Metropolitan tables.

Height-Weight Tables

The Metropolitan Life Insurance Company has got credit to develop the first height-weight tables to calculate the degree of individuals over or under weight status, in 1953. The data was based on “average” from its client base for men and women. In 1983 the tables were revised based on updated data.

Frame size is an important, subjective factor utilized in the development of the tables with small, medium and large frame determination changing the “ideal weight” recommendation. Improvement of frame size determinations were implemented in 1986 with the elbow breadth or wrist circumference measurement used to classify frame size.

The use of the Metropolitan height/weight table gives no indication as to the degree of either obesity or learners on an individual’s basis. In the individual clinic setting, height/weight tables car provide grossly inaccurate conclusions about are individuals’ health risk. The validity of estimation of percent body fat and density by height and weight measurement when compared to the Hydrostatic tank is very poor with correlation coefficients in the range 31 to 43.

Hydrostatic Weighing

It is currently considered that the hydrostatic weighing is the “Gold Standard” of body composition analysis Hydrostatic measurements are based on the assumption that density and specific gravity of learn tissue if greater than that of fat tissue. Thus, lean tissue will sink in water and fat tissue will float. By comparing a test subject’s mass measured under water and out of the water, body composition may be calculated.

The “Gold Standard” of body composition is a mathematical prediction. There are several limitations to the hydrostatic weighing technique. The equipment required to perform hydrostatic measurements is bulky and maintenance intense. A large tank of water, usually 1000 gallons, must be maintained at a constant temperature. Equipment to measure residual lung volume must be utilized.

A calibrated autopsy scale or its electronic equipment, connected to an “under-water chair” is also required. Test subjects are asked to exhale as much an­as possible from their lungs and the immersed for 10 to 15 seconds for an underwater weight measurement to be taken. This procedure is repeated 7 to 10 times. Total test procedures may require 45 minutes to one hour.

The accepted test re-rest of hydrostatic weighing is ±2.5% for comparison of consecutive tests with the same subject and the same technician. In non-controlled settings the test re-test variable may be significantly higher. Most of the variable may be significantly higher. Most of the variance is accounted for from a lack of subject cooperation and a lack of technician discipline and/or experience. Many tanks have not been critically examined for their test/re-test results.

Hydrostatic weighing methodology assumes that the density of bone in humans is constant. Thus, differences in bone density will create test errors. African-Americans and trained athletes are now known to have a higher bone density then non-athlete Caucasians.

The elderly and Asians have consider lower bone density. Specialized equations have been developed for use with African- American population. Fear of immersion, fear of infection, obesity and infirmity are additional barriers to the Hydrostatic measurement of accurate body composition analysis.

Skin-Fold Measurements

Skin fold Measurements are used to estimate the body fat. The test methodology requires the use of a “caliper device” to measure the thickness of substantial fat stores. The assumption is that substantial fat is proportional to over all body fat and thus by measuring several sites total body fat may be calculated.

There are many site measurements where skin fold measurements can be taken. Currently over 100 different equations are available to estimate body fat with the use of skin fold calipers. The wide variety of equations reflects the problem with the accuracy of this methodology.

There are many limitations with the Skin Fold measurement technique. The validity of skin fold measurements is at best ±6% compared to the hydrostatic tank. Because of the inaccuracy associated with skin fold calipers, many credible organizations have abandoned the use of them.

The estimation results obtained from skin fold measurement vary widely from technician to technician. The “art” of skin fold measurements requires the technician to properly identify a site measurement and pinch the skin gathering only that fat store and no other tissue. The error of estimate between technicians has been reported to be ±8%.

The obese population represents unique limitations for skin fold measurements. Skin fold calipers cannot open wide enough to measure the total fat thickness, thus tends to grossly under estimate body fat percentage in the obese population. Also of concern, especially in the obese population, is the compression of fat by the caliper due to variances in fat density.

Again, this tends to inaccurately estimate percent fat in the obese, the population where accuracy is most important. The assumption that 50% of human body fat is located in subcutaneal tissue and the remaining 50% is found in intra-muscular and essential fat (around organs) is not universally valid. Body fat distribution and health risk varies depending on genetics, exercise and nutritional patterns.

Near Infrared Interactance

It is, first developed by U.S.D.P. and used to measure fat. The U.S.D.A developed the technique to measure the fat contained in 1 cubic centimeter sections of beef and pork carcasses after slaughter. In the human device, a “wand” from the device er lits on IR light source at about 900 nanometers into the biceps area.

The methodology is based on the ability of fat tissues to “absorb” more IR light then lean tissue which can then be measured as a change in the infrared level. The only commercially available unit to predict human body composition is manufactured by Futrex. Since the Futrex device was first marketed for clinical use, many research articles have been published stating that the device is not accurate and is not recommended for clinical use in the assessment of body composition.

The original application of this IR technology was developed on “skinned” carcasses. No research is available about IR penetration through the skin. The actual contribution of the IR wand measurement and input the height and weight calculators used in the device’s program have also been questioned. This device has not been approved by the FDA for use.

Anthropometric Measurements

1. It is a quick, easy and inexpensive method to estimate body composition.

2. Using a standard calibrated cloth tape, girth and length measurements are taken from specific I points on the body.

3. The methodology is based on the assumption that body fat is distributed at various sites on the body such as the waist, neck and thigh.

4. Muscle tissue is usually located at anatomical locations such as the biceps, forearm and calf.

5. The subjects’ weight, height girth size and rations of various site comparisons are utilized in the calculations of percent body fat.

6. Although the use of anthropomorphic measurements provide a reasonably reproducible value and gives as topographical assessment of an individual, the established accuracy for the prediction of body fat is at least +5% compared to the hydrostatic tank.

7. Anthro-Electro Lipo Graphy, the new state of the art technology, utilizes the algorithmic approach of Electro Lipo Graphy (ELG) coupled with specific anthropomorphic measurements.

8. This technique was developed by BioAnalogica to further improve the original, patented algorithmic formula.

9. A total of five (5) to six (6) site measurements are entered into the algorithmic formula to increase the correlation coefficient to 0.91, and to reduce the standard error of estimate to ±2.8 compared to the hydrostatic tank.

10. No other clinically available unit provides the scientific accuracy, reliability and efficiency across a wide range of subjects.