One of the questions I see a lot of is what type of body fat analysis method is the most accurate and preferred? Well, like anything in the fitness world, ask 10 different people and you’ll likely get 10 different answers. Hopefully my personal experiences and research will help you understand why to pick one over other.
The skinfold estimation methods are based on a skinfold test, also known as a pinch test, whereby a pinch of skin is measured by specially designed calipers at several standardized points on the body to determine the subcutaneous fat layer thickness. These measurements are converted to an estimated body fat percentage by an equation. The accuracy of these estimates is more dependent on a person's unique body fat distribution than on the number of sites measured. As well, it is important to test in a precise location with a fixed pressure. Although it may not give an accurate reading of real body fat percentage, it is a reliable measure of body composition change over a period of time, provided the test is carried out by the same person with the same technique. Just to reiterate, it’s not the most accurate, BUT a good method of monitoring progress and change as long as the same person performs the test.
Another popular method is what’s called Bioelectrical Impedence. By standing barefoot on metal foot plates (as well as “gripping” a device), an undetectably low voltage electric current is sent up one leg and down the other. Since fat is a very poor conductor of electricity, a lot of fat will impede the current more than lean tissue. By measuring the resistance to the current, the machine estimates the percent body fat.
If done correctly on properly operating equipment, this method is approximately +/- 3%. However, accuracy depends upon several client-based variables. It is recommended the following guidelines be followed:
- Abstain from eating and drinking within 4 hours of the test
- Avoid exercising within 12 hours of the test
- Urinate completely prior to testing
- Do not drink alcohol within 48 hours of the test
- Avoid taking diuretics prior to testing unless instructed by your physician
- Requires little or no technical knowledge of the operator or the client
- Testing itself takes less than a minute
- The unit can be easily transported from place to place
- Requires only an electrical outlet and the machine itself
- This method has a higher standard error range than most people desire
- Tends to consistently overestimate lean people and underestimate obese people
- The accuracy BIA does have is very dependent on multiple variables which may be hard to control for some people
Note the disadvantages- higher standard error range and tends to OVERESTIMATE lean people and underestimate obese people. Not the most accurate method to go by.
An option to measure the fat content of a human body is to dissect a cadaver, remove the fatty tissue, extract the fat with a solvent and weigh the extracted fat. Only a very small number of human cadavers, widely varying in fatness and hydration level, have ever been analyzed in this way. However, certain data from these cadaver studies provide a good basis for estimating the body fat content in a living person. Irrespective of the location from which they are obtained, the fat cells in humans are composed almost entirely of pure triglycerides with an average density of about 0.9 kilograms per liter. Most modern body composition laboratories today use the value of 1.1 kilograms per liter for the density of the “fat free mass”, a theoretical tissue composed of 72% water (density = 0.993), 21% protein (density = 1.340) and 7% mineral (density = 3.000) by weight. If a body consists of a mixture of only two components, fat and the fat free mass, then the percentage of weight from fat can be calculated from the overall body density by the following equation:
- Body Fat Percentage = (495 ÷ Body Density) - 450
With a well-engineered weighing system, body density can be determined with great accuracy by completely submerging a person in water and calculating the volume of the displaced water from the weight of the displaced water. A correction is made for the buoyancy of air in the lungs and other gases in the body spaces. If there were no error whatsoever in measuring body density, the uncertainty in fat estimation would be about ± 3.8% of the body weight.
Estimation of body fat percentage from underwater weighing has long been considered to be the best method available, especially in consideration of the cost and simplicity of the equipment. Underwater weighing gives an actual measurement of body density rather than a prediction. But unless you live near a lab or University, having access to this method is going to be tough.
So in conclusion, these are just a few of the methods to measuring one’s body fat percentage. At Premier Fitness, we only do skinfold tests, simply based on the fact that it is the most consistent and cost effective. If someone presents a “device” for you to hold onto or stand on and says this is the most accurate method, I urge you to ask them about the above guidelines before performing the test, especially since you’ll likely be paying some sort of cost. At the end of the day, the mirror doesn’t lie and will always be the best measurement.