Body Composition Testing: My DEXA Scan Experience

In the world of nutrition and fitness, weight loss is a common goal for the majority of the general population. So much so that in fact individuals perseverate on it while overlooking other body composition metrics such as lean mass and body fat percentage.

While weight loss is a good general indicator of improvement in body composition, it is not the end all be all. Depending on your training history and methodology (i.e. resistance exercise vs aerobic exercise) there are other physiological changes that take place.

So we know that weight is unmistakably measured on a scale, but how do we measure other metrics such as body fat, lean mass and bone mass?

The Predominant Body Composition Testing Methods

1. Skinfold testing
2. Bioelectrical Impedance
3. Hydrostatic (Underwater)Weighing
4. Air-Displacement Plethysmography (BODPOD)
5. DEXA (Dual-Energy X-Ray Absorptiometry)

Skinfold Testing

Arguably the most affordable method of body comp testing is skinfold testing using skin calipers. Skinfold testing involves taking a device known as a caliper, pinching the skin and fat underneath the skin (known as subcutaneous fat), pulling the skinfold away from the underlying muscle, and measuring the thickness of the skinfold with the caliper. (1) Usually this is done on several standard sites on the body. The measurement is then plugged into an equation which gives you estimated fat mass and fat-free mass percentage.

Pros

• Most affordable
• Can be learned relatively quickly

Cons

• Accuracy depends on skill of technician
• More of a prediction as opposed to a concrete measurement

Bioelectrical Impedance

Another relatively quick and convenient method of measuring body comp is BIA. BIA involves running a mild electrical current through your body using various stick-on leads. Lean body mass has contains mostly water and body fat contains minimal water. Therefore, by determining resistance of the current running through your body, an estimation can be made as to how much fat-free mass and body fat mass you have. (2) Scales that also measure body composition, such as this, also would fall into this category.

Pros

• Quick and easy
• Fairly inexpensive to have done

Cons

• Questionable accuracy
• Affected by individual’s hydration status

Hydrostatic (Underwater) Weighing

The next method that is commonly used to measure body composition is underwater or hydrostatic weighing. In hydrostatic weighing, you are weighed underwater while simultaneously measuring amount of water displaced. Water displacement equates to body volume. Fat-free mass is more dense than fat; it weighs more for a given volume. Additionally, fat tends to float in water, while fat-free mass tends to sink. These principles are used to caculate your body density and this number is subsequently used to estimate your fat and fat-free mass. (3)

Pros

• Slightly more accurate than above methods

Cons

• Uncomfortable process
• Room for errors related to air bubbles in swimsuit or hair

Air-Displacement Plethysmography (BODPOD)

Another common method of body comp testing is the BODPOD. The test takes place by enclosing the individual in a small ‘air pod’ in which air is blown over and around them. This method is quite similar to hydrostatic weighing, though instead of determining how much water you displace, we are determining how much air you displace, while simultaneously weighing you. These numbers are then used to measure body density and plugged in to an equation to measure fat free mass and fat mass. (4)

Pros

• More comfortable than hydrostatic weighing
• Quick results

Cons

• Slightly less accurate than hydrostatic weighing
• More variables that can affect the results (facial hair, body temperature, moisture, clothing tightness)

DEXA (Dual-Energy X-Ray Absorptiometry)

While all of the previous methods divided the body into two compartments (fat and fat-free mass), the DEXA scan divides the body into three compartments (fat, bone mineral, and all other fat-free mass that does not include bone). When getting a DEXA scan you are instructed to lay on a special table where two different types of x-rays are passed through your body. This measures your body’s absorbance of x-rays at two different energies.  Fat, bone mineral, and fat-free soft tissue have different absorption properties. In turn, estimates of your body composition can be made by scanning your entire body. (5) This process takes only 5-10 minutes. DEXA scans are also used in the clinical setting for determining bone mass and diagnosing osteoporosis/osteopenia.

Pros

• 3-compartment model
• Very fast, easy and comfortable

Cons

• Results can vary with overall hydration status
• Inconsistencies in results between different machines from different manufacturers

A few months back I was approached by a representative from DEXAscan.com, the leader in DEXA scans within the United States with locations around the world. I was offered a scan in exchange for an honest review of the process and results. I arrived at the facility for my appointment and was briefed on the process. I was instructed to lay on the table in a specific position for optimal results. The x-ray arm then slowly passed over my body until it reached my feet. The test then finished up and I had the results with 10 minutes of laying down on the table. For some reason I though it would take longer and that I would have to take my clothes off but this was not the case. It was extremely easy and comfortable. Click here to see my results! 

Who Should Get Body Comp Testing

While body composition testing is not necessary by any means, it provides some helpful metrics to track your progress. At the end of the day, body comp testing is a prediction, the accuracy of which can vary, as you have seen. The only true way to determine body fat% and muscle mass would be to separate and weigh those respective tissues, of course you couldn’t be alive for that (LOL). Body comp testing, and especially DEXA scans can be a great tool to quantify all that hard work you put in towards diet and exercise. If you are interested in getting a DEXA check out the DEXAscan.com website for a location near you.

Have you ever gotten your body composition tested by any of the above methods? Would love to hear about your experience. Please comment below. And until next time my friends, BE ELITE!

References

1. https://weightology.net/the-pitfalls-of-body-fat-measurement-part-5-skinfolds/
2. https://weightology.net/the-pitfalls-of-bodyfat-measurement-part-4-bioelectrical-impedance-bia/
3. https://weightology.net/the-pitfalls-of-body-fat-measurement-part-2/
4. https://weightology.net/the-pitfalls-of-body-fat-measurement-part-3-bod-pod/
5. https://weightology.net/the-pitfalls-of-body-fat-measurement-part-6-dexa/