Why Measure Body Fat At All?

Percent body fat is known to be a key factor in determining fitness. It is also a known indicator of disease risk. Weight alone is not a reliable indicator of good health. Weight (pounds on the scale) does not distinguish between pounds that come from body fat and those that come from lean body mass or muscle. Carrying too much fat is what makes a person obese. Obesity is a known risk for many serious medical conditions including heart disease, diabetes and even certain forms of cancer. Obesity contributes to at least half the chronic diseases in western society.

Why Use Near Infrared Light?

NIR Quantitative Analysis was developed by the United States Department of Agriculture (USDA) in 1970. A simple non-destructive method of providing measurements of organic constituents was needed. The USDA discovered that when light is shined through any type of organic item, each item had its own, unique “glow.” The first NIR applications were agricultural, measuring sweetness in fruit, fat levels in ground beef, and protein levels in grain products. Futrex took the principles of NIR analysis, and adapted them for the measurement of percent body fat.

How Does The Futrex Measure Body Fat?

US government research determined that the biceps of the dominant arm has a direct correlation with overall body fat. Futrex’s technology uses Near-Infrared Interactance. This is the same technology used in the remote controls of modern TVs. Body fat absorbs these wavelengths of light and lean mass reflects them. The light absorption and reflection is measured to determine body fat.

What Does the Futrex “See” With NIR?

Fat – NIR light is absorbed by fat Subcutaneous fat Inter-muscular fat Lean Mass – NIR light is reflected by lean mass Muscle Bone Water

How & Why Does Futrex Work?

The FUTREX actually performs optical measurements. The Futrex Wand sends measured amounts of NIR light into the biceps of the dominant arm. Varying amount of light is absorbed or reflected, providing “optical density” values. Inputs them into a proprietary formula – (Multiple Linear Regression Analysis). Displays total body fat (TBF).

Why a Single Site Measurement?

USDA research found that the ratio of fat to lean mass is best represented in the inter/intra muscular region of the body. Three such locations were identified: Mid point of the Biceps Mid point of the Triceps Mid point of the Quadriceps Futrex chose the biceps for convenience

How Accurate is the Futrex?

Underwater Weighing is known as the “Gold Standard” of body fat measurement. Many people refer to it as the “dunk test.” All other methods, including Futrex, are calibrated to to this “reference laboratory.” Underwater Weighing has a Margin of Error of plus or minus 3%. Futrex has the same margin of error as Underwater Weighing.

How Does Futrex Compare to Other Methods?

All methods of body composition analysis are evaluated against the “Gold Standards” of Underwater Weighing or DEXA. All methods (BIA, skinfolds, FUTREX) have been shown to have accuracy similar to the “Gold Standards” in a clinical/research environment.

A major concern of researchers, however, is that the accuracy and repeatability can be affected by changing field conditions:

Skin fold calipers have been shown to have up to 9 percent variability from differences in skin fold technicians. (1)
Bio-Electrical Impedance requires the following pre-test protocols (2):

  • No alcohol 48 hours before the test
  • Avoid intense exercise 12 hours before the test
  • Avoid eating or drinking (especially coffee, tea, and colas) 4 hours before the test
  • Empty bladder 30 minutes before test
  • Avoid all diuretics for 7 days before test (only if possible)

The NIR technology used by Futrex, eliminates theses concerns, making it both accurate and repeatable.

  1. Morrow, J.R., T. Fridye and S.D. Nonaghen. Generalizability of the AAPHERD health related skinfold test. Research Quarterly for Exercise and Sport 57: 187-195, 1986.
  2. Vivian H. Heyward and Lisa M. Stolarczyk, Applied Body Composition Assessment, (Champaign: Human Kinetics, 1996) 54.