30-Second Overview: Measuring Body Composition

Here’s a 30-second summary on the 5 procedures for doing Body Fat Analysis.  This is different from Body-Mass-Index (BMI), which is a correlation between a person’s height and weight, as determined by a formula. Skinfold Caliper – can be done by most trained health professionals or fitness professionals – this is one you see in the gym most often.  Quick and easy.  Usually requires taking three measurements at different sites of the body (tricep, abdomen, upper thigh) then plugging these numbers into a formula.  However…May be 7-8% error in measurement. Measurements can be affected by the skill level of the professional taking them and are not accurate for obese patients.

Bioelectrical Impedance – fairly inexpensive scales or handheld devices are now available for purchase and use in the home.  The device sends a tiny electrical impulse through the body and measures the body fat by how easily the impulse is transmitted.  These devices are good to give you a sense of how your body fat may change over time but are not highly accurate.  Readings can be easily affected by hydration status, obesity, and muscle mass.  Muscular athletes typically get higher than actual results because their body composition can be outside the normal statistical range that the formula is geared to.

Underwater Weighing – this requires that you be completely submerged in a tank of water. While underwater you must breathe out all air from your lungs.  It requires specialized equipment and highly trained technicians.  When performed correctly it as a less than 2% error rate.

DEXA – stands for “dual x-ray absorptiometry”. Is quick and easy but requires expensive equipment typically only found in hospitals and research centers. It takes an x-ray of the body that shows fat, muscle, and bone mass based on differing densities. It has very good accuracy.

Bod Pod – still fairly new on the market but seems to have great promise. Studies show it to be comparable to underwater weighing and DEXA. The major advantages are that it is fairly inexpensive equipment, requires little training to operate, comfortable for people of all shapes and sizes, and is quick and easy. All you do is have a seat in an enclosed egg-shaped pod.  (Content note: Our thanks to University of Texas Southwest Medical Center in Dallas / Nutrition Tips Sheets)