Near Infrared Interactance is one of many measures of body composition, which uses a computerized spectrophotometer, which has a single, rapid scanning monochromator and fiber optic probe. This method uses the principles of light absorption and reflection to measure body fat.
equipment required: computerized spectrophotometer
pre-test: Explain the test procedures to the subject. Perform screening of health risks and obtain informed consent. Prepare forms and record basic information such as age, height, body weight, gender and test conditions. See more details of pre-test procedures.
procedure: The measurement is taken on the person's dominant arm. A monochromator, or light "wand", sends a low-energy beam of near-infrared light into the biceps and penetrates the underlying tissue to a depth of one centimeter. The energy is either reflected, absorbed, or transmitted, depending on the scattering and absorption properties of the biceps. A detector within the wand measures the intensity of the re-emitted light. Shifts in the wavelength of the reflected beam and a prediction equation are used to compute the percent body fat.
advantages: The measurement is safe and the equipment is portable and lightweight. It requires little training to use.
disadvantages: This technique still lacks validation in humans, and may not accurately predict body fat across a broad range of fat levels. It assumes fat in the arm is proportional to total body fat, which may not be true.
other comments: This method is based on what was developed by the United States Department of Agriculture to measure the body composition of livestock and the fat content of various grains.
products: Futrex: uses Near-Infrared light to directly measure percent body fat
- Dual-Energy X-Ray Absorptiometry (DEXA) — using this method you can determine body components including non fat soft tissue.
- Total Body Potassium (TBK) accurately determines the body's total cell mass (that is, the active growing tissues in the body), which in turn can be used to estimate fat-free or lean body mass. When this measurement is combined with measurements from the Total Body Protein, you can determine total organ and muscle mass.
- Magnetic Resonance Imaging (MRI) — with MRI it is possible to get accurate measurements of the composition of body tissue, by identifying muscle, fat and organs etc.
- Total Body Electrical Conductivity (TOBEC) — can be used to estimate lean body mass.
- Computed Tomography (CT) — the high quality images can be processed to differentiate and measure the amounts of fat and lean body tissue.