Hand-held body fat analyzers that use near-infrared interactance (NIR) technology typically measure fat in a single body area — such as the bicep. The standard error estimate for this method is ¬+5% body fat; that’s pretty high. So, while you’ll often see these gadgets at health fairs and gyms, they’re not recommended for use in most populations.
There are also hand-held devices that measure body fat via bioelectrical impedance, a method considered to be reasonably accurate, with a standard error estimate falling between +2.7 and 6.3%. Because hydration status affects results, the user should follow manufacturer instructions regarding eating, drinking, and exercising prior to measurement.
Skinfold measurements, when taken by a skilled technician using a high-quality caliper, offers a standard error estimate of only +3.5%. Keep in mind that acquiring a reliable level of skill in this technique requires specific training, experience in testing hundreds of people and regular practice — but it’s worth your time and effort, because this is a relatively quick assessment you can perform in a variety of settings. The ACE Personal Trainer Manual, 4th edition contains detailed procedures and photos of skinfold sites to help you learn more about this widely-used body composition assessment technique.