How Do Body Composition Scales Work and How Accurate Are They?
Weight scales have proven to be reliable tools for monitoring one’s weight. However, they cannot tell what percentage of their measurement is muscle, fat, or water weight. To accurately know these percentages, you’d have to get a Dual-Energy X-Ray Absorptiometry (DEXA) scan—which is only available at clinics.
A more convenient way to measure body fat, muscle, and water weight percentages is to use a body fat, or body composition, scale. With these scales, you can finally learn your body composition within the comforts of your home. But how accurate are these scales, and can you really trust the results?
How Body Fat/Composition Scales Work
Body fat scales measure body weight percentages using Bioelectric Impedance Analysis (BIA). This test can analyze your body composition by sending weak electrical pulses through your body. If you look at a body fat scale, you’ll notice two pairs of metallic plates (usually circles). These plates are conductive and are used to send and receive the electrical pulse from one foot to the other.
By sending a weak direct current through your body, the scale gains enough information to give you your weight percentages. This current will always be at a fixed value. When the electric pulse finally returns to the other pair of conductive plates, the scale then measures your body’s resistance by sensing how much weaker the pulse got after it traveled through your body.
Once the scale knows your body weight and resistance values, it runs these numbers through a proprietary mathematical equation formulated by the scale’s manufacturer. The results are then compared to a look-up table, upon which your weight percentages will be based. Some body fat scales may also use an external database where data is collected from every user using the scale. These collected data are then used to form a user database which can increase the accuracy of the scale’s reading.
How Accurate Are Body Composition Scales?
BIA relies heavily on being able to read resistance to measure your body composition. This presents a few problems, as body impedance and resistance can change depending on the time of day, water intake, and even foot calluses.
Aside from body impedance, your overall body weight is another key part of the equation needed to extrapolate your weight percentages. But your weight changes depending on the time of day, water intake, food intake, clothes you wear, and even the evenness of the floor where the scale is placed.
Electricity also has a characteristic where it will always travel the shortest route to reach ground (in this case, the other pair of conductive plates). So, the electric pulse will only travel from one foot to the other without necessarily going up to our upper body. This means that these types of scales may only measure the impedance and resistance of the lower half of your body.
Another factor that affects the accuracy of your scale is the proprietary mathematical formula it uses. If you are interested in evaluating the formula yourself, some of the more reputable brands provide their formulas on their websites. However, for many body-fat scales on the market, you’ll have to trust that their formula is sound.
So, are body fat scales accurate? Considering the limitations of BIA and other factors that may affect that scale’s readings, consumer body fat scales are likely not very accurate. They’re definitely not as accurate as a DEXA scan. However, these scales may have some use if you follow the tips below to make your readings as consistent as possible.
Making a Body Fat Scale Reading as Accurate as Possible
As discussed earlier, many of the problems with body fat scales are based on how a person uses the scale. To use the scale as accurately as possible and ensure consistent readings, follow these tips:
- Make sure your scale is placed on an even surface.
- Do not wear socks or shoes when measuring body composition.
- Wear as little clothing as possible or be consistent with the number of clothes your wear when measuring.
- Use the scale before drinking your first glass of water for the day, and before you eat anything.
- Be consistent with what time you use the scale.
If you’re careful about how you measure yourself and track the data consistently, you may find some benefit from monitoring changes in your body composition based on a fitness program or diet. However, it’s important to remember that many variables can affect the readings, so you should only treat them as rough estimates that are possibly inaccurate and definitely don’t tell the full story.
Should You Buy a Body Composition Scale?
If you have a few dollars to spare and were already shopping for a regular weight scale, buying a body composition scale could be useful to help with your fitness goals. While it’s true that these scales are not as accurate when compared to a DEXA scan, they can help you better understand some general characteristics of your body. However, there are better ways to track health metrics, like wearing a fitness tracker.
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September 21, 2022 at 07:22AM