How Is It Measured?

Step Off of the Bathroom Scale… Forever!

Over the years a number of methods have been developed to measure body composition. Until the BOD POD, all of these methods had drawbacks, being inaccurate, messy, difficult, require extensive training, or invasive.

In measuring body composition, it’s not only important what the result is, but also how you arrived at it. For example, let’s say you’re a woman with a skinfold or bioelectric impedance body fat measurement of 22%. At first glance it seems that you fall into a healthy body fat range. The problem is, since the error factor for both of these methods is up to +/-8%, this number could mean your actual body fat could be as low as 14% (risky – low body fat) or as high as 30% (borderline excess fat). Inaccurate information like this is no better than no information at all, and can be downright dangerous if being used to determine an appropriate diet and/or training program. This is why it’s so important to receive an accurate body composition assessment. It’s the only way to get the proper information necessary for making sensible decisions regarding nutrition and fitness programs.

Comparison of the various methods for assessing body composition

BOD POD
Based on the same whole-body measurement principal as hydrostatic weighing, but using patented air displacement technology instead of water. The subject sits comfortably inside the BOD POD while computerized pressure sensors determine the amount of air displaced by the person’s body. Testing is highly accurate, safe, and quick, with a complete analysis in about 5 minutes.

Advantages:

• Uses the most advanced technology available today.
• Based on proven accurate whole body measurement principle.
• Fast test time (about 5 minutes).
• Easy and suitable for all types of populations including the obese, disabled, elderly, and children.
• Provides excellent repeatability and tracking.
• Non-invasive.
• Almost no equipment maintenance.
• Error rate is less than 2%

Disadvantages: None

Hydrostatic Weighing (“Dunk Tank”)
Based on the whole-body principle of Archimedes, which states that the volume of an object is equal to the object’s loss of weight in water, with a correction for the density of the water. In this procedure the subject is required to sit strapped in a chair that is submerged into a water tank and weighed. While submerged, the subject must expel all the air from their lungs and hold their breath for 10-15 seconds until the scale can be read. This process is repeated up to 10 times to ensure accuracy.

Advantages:

• Has long been considered the “gold standard” of body composition measurement.
• Known to be very accurate when compliance issues can be followed properly.
• Error rate is less than 2% under proper conditions.

Disadvantages:

• Testing is lengthy (up to 1 hour), arduous, and very difficult to perform correctly.
• Technician must be highly skilled in order to obtain accurate results.
• Some populations are impossible to test, including the extremely obese, disabled, elderly, and those with an aversion to water.
• Maintenance issues are high. Water temperature needs to remain constant and the tank should be drained after each measurement (dirty water can skew results).

Dual Energy X-Ray Absorptiometry (DEXA)
In this procedure the subject lies on a table and the body is slowly scanned. Computer software then reconstructs an image of the underlying tissue to determine total fat and lean mass.

Advantages:

• Under proper conditions it provides very good results.
• Comfortable.
• Error rate is less than 2% under proper conditions.

Disadvantages:

• Uses x-ray technology, which is invasive.
• Equipment is very expensive – from $60,000 to $100,000, and almost exclusive to medical facilities.
• Limited Use X-Ray Technician license required for the operator.
• Different DEXA equipment can produce different results.
• Testing can take up to 20 minutes.
• Not accurate in testing the extremely obese.

Skinfold Calipers
Measures subcutaneous fat at several sites on the body by pinching the skin with calipers.

Advantages:

• Portable and easily performed in the field.
• Inexpensive

Disadvantages:

• Not as accurate as most other methods, since only subcutaneous fat is being measured. The assumption is that subcutaneous fat is proportional to a person’s total body fat, but this proportion actually varies quite a bit based upon gender, age, and ethnicity.
• Reliability is highly dependent upon the type of calipers used, the skill level of the technician, and the skinfold equation used (there are hundreds of them).
• Not a valid method for measuring the extremely obese.
• Testing can take a long time, as many sites need to be pinched repeatedly to achieve the most accurate result.
• Error factor of up to +/-8%.

Bioelectric Impedance Analysis
This method is based on the concept that the lean tissue of the body is more conductive than fat tissue due to its higher water content. Testing involves the placement of electrodes on the skin while a low dose electrical current is passed through the body. The resistance to this current is determined and converted to percent body fat.

Advantages:

• Testing is relatively quick, simple, and comfortable.

Disadvantages:

• Not as accurate as the BOD POD, hydrostatic weighing, or DEXA.
• Results are greatly affected by the type of instrumentation used, hydration level, food intake, and skin temperature.
• Can’t be used by those with medical implants such as pacemakers and defibrillators.
• Error factor of up to +/-8%.

Near Infrared Light Device (Futrex)
This method is based on the principle that all organic materials (e.g. fat or protein) absorb light in unique portions of the spectrum. Optical measurements at two wavelengths are taken along with physical characteristics of the client

Additional pages:
Frequently Asked Questions
How Is It Measured?
What Does It Mean?
What Is Body Composition and why is it Important?