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Measuring Body Fat with NIR (Near Infrared Interactance)

Measuring Body Fat with NIR (Near Infrared Interactance)

NIR (Near Infrared Interactance)

Most people now understand that to have a healthier body means to have a leaner body. These people are ready for Body Composition Analysis (BCA.) These pages will attempt to acquaint you with the most popular methods of BCA used in gyms, homes, and professional practices.

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 biceps is the most often used single site for estimating body fat using the NIR method. The NIR light penetrates the tissues and is reflected off the bone back to the detector. The NIR data is entered into a prediction equation with the person's height, weight, frame size, and level of activity to estimate the percent body fat.

This method has become popular outside of the laboratory because it is simple, fast, noninvasive, and the equipment is relatively inexpensive. However, the amount of pressure applied to the fiber optic probe during measurement may affect the values of optical densities, and skin color and hydration level may be potential sources of error. To date, studies conducted with this method have produced mixed results; a high degree of error has occurred with very lean and very obese people; and the validity of a single-site measurement at the biceps is questionable. Numerous sources report that more research is needed to substantiate the validity, accuracy and applicability of this method.

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