In addition to reporting your total body weight, a body fat scale takes into account your body composition, or the percentage of body fat compared to your lean body mass (muscle, bone, etc.).
This can give you a more complete picture of your relative health risk and be helpful as you work towards achieving it.body recomposition, which occurs when you lose body fat while gaining muscle mass.
But are body fat scales accurate? How do body fat scales measure body fat percentage?
In this article, we look at body fat scale accuracy, how body fat scales measure body fat percentage, and whether there are better options.Measuring your body fat percentagethan with a body fat scale.
We will cover:
- What does a body fat scale measure?
- How do scales measure body fat percentage?
- Are body fat scales accurate?
- What affects the accuracy of the body fat scale?
Lets go in!
What does a body fat scale measure?
Before examining body fat scale accuracy, it's helpful to briefly review what exactly body fat scales measure.
That's what a body fat scale is designed for.Analyze your body fat percentage.
Body fat percentage refers to the relative amount of your body weight that is made up of adipose tissue or fat relative to lean body mass, which is basically any type of tissue other than body fat (bones, nerves, connective tissue). . , blood , organs). , skin, etc.).
Your body fat percentage is one of the indicators of your overall health and risk of certain diseases.
Laut der University of Pennsylvania, the average percentage of body fat for a healthy adult, regardless of age, is 15-20% for men and 20-25% for women.
How do scales measure body fat percentage?
So how do body fat scales work? How does the body fat scale measure your body fat percentage?
Body fat percentage is determined on a body fat scale using a method known asbioelectrical impedance
When stepping on a body fat scale, you must remove your socks and shoes so that your bare feet come into contact with the scale's electrodes.
In bioelectrical impedance, a safe, low-intensity electrical current is passed through your body.
The principle behind this method of analyzing body fat percentage is that an electrical current flows through body fat and lean tissue at different rates because the resistance of these tissues to the electrical current is not equal.
The electric current emitted by the scale flows more easily through body tissues with a higher water content (blood, muscles, urine) than through dry tissues (fat and bones).
The body fat scale also takes things like height into account, so the time it takes for the chain to rise on one side of your body and fall on the other is fed into an algorithm that can determine your body fat percentage based on your size. it's time. it took a while for the signal to travel through his body.
Essentially, the algorithm combines the measurement of bioelectrical impedance (how fast electrical current flows through your body) with other inputs such as total body weight, height, gender, age and possibly even your fitness level, depending on your fitness level. body fat quality. scale.
In general, the longer it takes for electrical current to travel up the leg on one side of the body and down the other, the higher your body fat percentage.
This is because the electric current encounters greater resistance when passing through dry tissue, such as fat, than when passing through muscle tissue.
Higher quality body fat scales also have a handle with metal electrodes attached to the body fat scale. The handle also emits an electrical current that travels to your torso.
The algorithm can then calculate a more accurate body fat percentage based on your torso's targeted bioelectrical impedance.Yslow body.
The general consensus is that body fat scale accuracy is significantly improved when the body fat scale has both an upper body and a lower body, as it can provide a more complete picture of the actual distribution of body fat.
Are body fat scales accurate?
While many people swear by the accuracy of a body fat scale, it's important to remember that a tool is only really useful if it's accurate.
Unfortunately, many studies have indicated that the accuracy of body fat scales is not as good as the manufacturers would like us to believe or as we would like to believe.
Most studies have found that body fat scales underestimate your body fat percentage, and the accuracy of a body fat scale can also depend on your current height and body fat percentage.
for example alearncompared the accuracy of three different body fat scales with the percentage of body fat determined by a DEXA scanner (an accurate medical imaging technique used to measure body composition).
Results showed that body fat percentage measurements provided by smart scales or body fat scales were not accurate when assessing body fat.
All three smart scales used underestimated both body fat percentage and absolute fat mass. For example, one of the scales underestimated absolute fat mass by 4.4 kg (almost 10 pounds!).
The degree of discrepancy between the body fat scale reading and the actual percentage of body fat determined by the DEXA scale was even greater in obese or overweight individuals.
This indicates that the accuracy of body fat scales may be even worse for overweight people.
other investigationssuggests that body fat scales can be similar in usefulness to body mass index (BMI) in that they can provide a reasonably good indication of body fat percentage for a population, but not necessarily for specific individuals.
Just as BMI generally classifies fit athletes as overweight or obese based on their muscle composition, the accuracy of the body fat scale appears to be low for overweight or obese individuals, but on average it can provide a decent estimate of the percentage of body fat for large groups (population vs. individuals). ).
However, since most people who use a body fat scale at home are only interested in measuring their personal body fat percentage, this isn't very useful for the average home user.
What affects the accuracy of the body fat scale?
There are numerous factors that can affect the accuracy of body fat measurements on a body fat scale.
Body fat scales that use foot-to-foot analysis exclusively are generally less accurate than those that include a strap because bioelectrical impedance ignores large parts of the body as it measures only the lower body.
The algorithm that the scale uses to calculate your total body fat percentage is extrapolated based on your lower body fat percentage only.
Depending on your personal pattern of body fat distribution, this may be too inaccurate for some people.
For example, if you have a traditional "apple-shaped" physique, where you store most of your fat in your abdomen (a typical male body fat distribution), these types of body fat scales may underestimate your body fat percentage. body because the scale will assume you are the same in your core and upper body is lean as in your legs.
On the other hand, if you have a "pear-shaped" physique, where you store more body fat in your hips and thighs, the body fat scale will overestimate your total body fat percentage because the algorithm calculates your total body fat percentage based on in your build and be just as "fat" in your upper body as you are in your hips and thighs.
Most studies indicate yes.Foot by foot body fat analysisfrequently overestimates body fat percentage in lean individuals and underestimates body fat percentage in overweight individuals.
In addition, the accuracy of the body fat scale is affectedyour hydration status. A higher fluid intake is reflected in a higher percentage of body fat because water resists electrical currents.
Therefore, it is important that you try to measure your body fat consistently relative to the time of day.hydrationand empty the bladder.
More accurate measurements of body fat can be obtained through DEXA scans and other medical or laboratory tests.
For home assessment, you can monitor changes in body composition using circumference measurements or a similar device.Zosophie, a body measurement system that uses 3D fit technology to help you track your changesbody compositionor the transformation of your body over time.
For more information on a healthy body fat percentage, see our guide:What is a healthy body fat percentage?