There are two methods you are most likely to come across are skinfold calipers and bioelectrical impedance the technology behind body fat scales. Although these methods aren’t inherently the most accurate, you can take precautions to make the results more trustworthy.
What is Skinfold Calipers?
Skinfold calipers, commonly used by fitness trainers and registered dietitians, look something like spring-loaded lobster claws. The tester pinches three to seven spots on your body, and a gauge measures each hunk of flesh in millimeters. The tester then plugs the result into an equation.
Calipers can be accurate within 4 percentage points but only if the tester is skilled at separating fat from muscle and pinches precisely the right spots. Even experienced testers can have difficulty testing subjects who have taut skin, especially on the thighs; considerable excess fat, especially in the abdominal area or highly developed muscles.
Also, accuracy may depend on the equation used, as different racial groups tend to carry fat in different places. And it’s important that the tester uses a formula that takes age into consideration. Fat tends to move inward with age, but calipers pinch only fat near the skin; so unless the tester uses a formula designed for seniors, the amount of fat pinched by the caliper in an older person might underestimate the person’s total body fat.
You can purchase do it yourself calipers over the internet, but you won’t get as accurate a reading as a trained professional would, and some experts think they are too inaccurate to be of use.
Bioelectrical Impedance is a quick painless method that comes in three varieties full body, lower body, and upper body. With full body impedance, offered by some trainers and nutritionists, you lie on your back while an electrical signal travels from an electrode on your foot to an electrode on your hand.
The faster the signal, the more muscular you are. This is because water conducts electricity, and muscle is 70 percent water fat contains a lot less water, so it impedes the signal.
When you step on a body fat scale, a signal travels through your lower body, from one foot to the other. When you hold the Omron, a plastic gizmo that looks like half of a car steering wheel, the signal shoots through our upper body, from hand to hand.
Even under optimal conditions, the margin of error for full body impedance is about 4 percent and perhaps 1 percent points more for the scale or upper body device. Since many people don’t experience changes in body fat of this magnitude, impedance methods may have a margin of error that’s too high to accurately detect body fat changes for the average person.
What’s more impedance gadgets are highly sensitive to hydration status. If you are dehydrated, the test can overestimate your body fat by as much as 10 percentage points. Also, impedance devices are typically less accurate for people who are obese or very lean.
For best results, get tested first thing the morning, before you have eaten or exercised but after you have normalized your hydration status with a glass of water. Women should avoid testing during menstruation because some retain water during the time.
