Body fat percentage measuring methods: NIR (Near Infrared Interactance)

A fiber optic probe is connected to a digital analyzer that indirectly measures the tissue composition (fat and water) at various sites on the body. This method is based on studies that show optical densities are linearly related to subcutaneous and total body fat. The NIR method of assessing body fat is based on the principles of light absorbtion , reflectance, and near infrared spectroscopy. To estimate body composition, a computerized spectrophotometer that has a scan and probe are used. The probe is placed onto a selected body site such as the biceps; it emitts an infrared light which passes through both fat and muscle and is reflected back to the probe. The NIR data is entered into a prediction equation with the person’s height, weight, sex, age, frame size, and level of activity to estimate the percent body fat. Density measurements are obtained and incorporated into the manufacturer’s prediction equations. A digital read out including percentage body fat and lean tissue are displayed.