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Kent Probst, BS, MEd
Kent Probst is the owner of Long Healthy Life Blog
What is a Body Composition Test?
A body composition test measures the percentage of body mass that is fat-free tissue and that which is fat. The benefits of a body composition test have numerous health implications.
The methods for measuring body composition vary regarding accuracy, cost and complexity.
The technician assessing body composition must be properly trained and have experience with the technique being used.
Keep in mind that any body composition test will not be exact, because with any measurement there is always chance and error involved.
Why is a Body Composition Test Important?
In addition to being at risk for type II diabetes, hypertension and cardiovascular disease, being overweight can lead to a host of other problems such as osteoarthritis, gout, sleep apnea, Alzheimer’s and several forms of cancer.
More than 70% of American adults are overweight, or obese, and more than 35% of American children are overweight or obese.
With a sedentary lifestyle, the problem gets worse.
Sarcopenia, the loss of muscle mass and strength due to age, as well as a loss of bone mineral mass, can make the ratio of fat mass to fat-free mass less desirable.
Sarcopenia increases the risk of falling, and osteoporosis increases the risk of fractures from falls.
Based on all the problems associated with being overweight and the loss of muscle mass, it’s important to know your body composition.
A body composition test will tell you approximately how much weight you need to lose if you’re overweight.
The benefits of a body composition test include determining if you’re losing muscle mass or gaining fat mass.
Chronic loss of muscle mass means that you’re burning fewer calories at rest.
If you’re an athlete or someone who is strength training, you may want to know how much muscle mass you’re gaining and how much fat you’re losing.
What is a Healthy Body Composition?
Healthy body composition varies depending on age and gender. A healthy body fat percentage for someone aged 20 – 29 is lower than someone aged 70 – 79.
A good range for men is 11.5% – 22.9%. And for women, a good range is 16.8% – 26.3%.
It’s not considered safe for men to go below 3% body fat. Women are not recommended to go below 10% – 13% body fat.
How to Measure Body Composition
Hydrostatic Weighing
Hydrodensitometry, or hydrostatic weighing, involves underwater weighing to measure whole-body density using the ratio of body mass to body density.
Underwater weighing is based on the Archimedes principle which states that a body immersed in water is buoyed up by an opposite force equal to the amount of displaced water.
Since bone and muscle are denser than fat, someone with less body fat will weigh more in water than someone with more fat, even though they weigh the same on land.
Although hydrodensitometry is a standard method for measuring body composition, to be as accurate as possible it should have the following:
- Excellent compliance from the test subject
- Accurate measurement of residual volume
- Correct use of body density conversion formulas
When done properly, underwater weighing can be accurate within a range of 1.8% – 2.8%.
Skinfold Test
The skinfold test estimates body fat percentage based on the measurements of several skinfold thicknesses across the body.
About one third of body fat is located subcutaneously, which is factored into the assessment.
The benefits of this body composition test are that it’s relatively easy to administer and it correlates well with underwater weighing and air displacement testing.
You’ll get the most accuracy from the skinfold test if the technician has ample training and experience.
The skinfold test accuracy for measuring body fat percentage is +3.5%.
Bioelectrical Impedance Analysis (BIA)
Bioelectrical Impedance is commonly used in health clubs and other fitness settings.
Its appeal is that it’s easy to administer and inexpensive. BIA measures the impedance of a benign electrical current through water in the body.
The accuracy of BIA is similar to the skinfold test.
The results of the BIA can be affected by the following factors:
- Positioning of electrodes
- Movement
- Hydration
People getting a BIA measurement should refrain from exercise several hours before the test.
The amount of water you consume before the test can also affect the results.
DXA Scan
Commonly used in clinic research, the DXA scan (Dual-Energy X-Ray Absorptiometry) is used less frequently for fitness testing due to cost, the need for highly trained technicians, and specialized equipment.
The DXA scan determines body composition by analyzing bone density, lean mass and fat tissue.
When it comes to measuring body composition, the accuracy of the DXA scan is close to 1%.
Air Displacement Bod Pod
Body composition testing by this method uses air-displacement plethysmography to measure body fat percentage.
The Bod Pod is administered quickly and easily, and requires no extensive training of the technician.
The person undergoing this assessment sits in the Bod Pod chamber, wearing minimal clothing such as a swimsuit. Each measurement lasts 35 – 45 seconds.
The standard range of error for the Bod Pod is +1% – 2.7% and can be as accurate as hydrostatic weighing.
How to Improve Body Composition
In addition to reducing your disease risk, maintaining a healthy body composition will pay dividends for years to come.
Cardiovascular exercise is a great way to reduce body fat.
The American College of Sports Medicine recommends 150 minutes per week of moderate intensity cardiovascular exercise, or 75 minutes per week of vigorous cardiovascular exercise to significantly reduce the risk of disease.
Strength training is also an intervention that will help improve body composition by increasing muscle mass. Increased muscle mass will allow you to burn more calories at rest.
Strength training should be done 2 -3 times per week to see the benefits of improved body composition
A great way to make sure you’re eating correctly and taking the proper nutritional supplements while improving your body composition is to consult a registered dietitian who specializes in sports nutrition.
With cardiovascular exercise, strength training and proper diet, you can enjoy the benefits of improved body composition.
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