Are Smart Scales Accurate? The Science Behind Their Claims

When my old scale broke, I was not very eager to purchase a new one. Who finds shopping for scales exciting?

But this is when I came across a wide selection of so-called smart scales: scales offering more insights into your body metrics than overall body weight. Although the promises made by their manufacturers sounded somewhat gimmicky, I instantly saw the appeal especially since I was just starting strength training and aiming to gain more muscle mass.

And since I was curious, I got one myself. Besides that, the price tag between a smart scale and a regular one is sometimes rather similar, so why not invest in something that could give me more detailed information about my body composition?

Now, after owning mine for over a year, I am revisiting the question: are smart scales accurate? In this article, you will learn all the science says about smart scales (spoiler alert — not much) and things to consider before you buy one.

How do smart scales work?

Before examining their accuracy, I began my research on how smart scales measure the things they claim to measure.

Besides traditional weight measuring, the leading technology used in smart scales is a bioelectrical impedance meter. When you use the smart scale, it sends a low-level electric current through your body. Fat tissue resists this current, while the electrolytes in body water allow the current to pass. This difference in resistance enables the device to estimate your body composition.

It is also important to mention that to measure body composition and other metrics, smart scales use various formulas and algorithms. Other factors that may influence the accuracy of the smart scale include the quality and number of sensors. A higher number of sensors (hand and foot) tends to provide more accurate measurements.

What do smart scales measure?

While not all smart scales are made equal, most of them allow you to track the following metrics.

Body weight

The first measurement is simply the overall body weight. It is the main metric tracked in weight management, although it could be argued that people usually tend to desire fat mass loss, not just overall weight loss.

Body fat percentage

The primary difference between a traditional scale and a smart one is that smart scales can measure body fat. Tracking body fat percentage is especially useful for those who are simultaneously building muscle and trying to lose fat, as the overall body weight might not change much.

Visceral fat

Visceral fat is fat stored around your internal organs. It is deemed more dangerous than subcutaneous fat (or fat that is located under one’s skin and can be pinched with fingers). Many smart scales indicate the estimated level of visceral fat and categorize it as either low, medium, or high.

Muscle mass

Muscle mass refers to the amount of muscle tissue in your body. Gaining skeletal muscle mass is one of the primary goals of working out, so many people consider this metric to be one of the selling points for smart scales.

Bone mass and density

This measurement indicates estimated skeletal weight. While bone density and mass do not fluctuate much in adults, people who have a higher risk of osteoporosis might want to keep an eye on it. However, for a more precise evaluation, you would need to have a DEXA scan, as a smart scale is not a diagnostic tool.

Body mass index (BMI)

Some smart scale apps also calculate your body mass index, which is derived from your total mass (weight) and height. Keep in mind since your height is used to compute this number, you have to specify the correct height for the metric to be accurate.

Metabolic age

Lastly, within the fitness apps, you may also find age as a metric — but it does not refer to your biological age. With the data collected, the app will estimate your metabolic health and put you in a certain age group. Lower age reading might indicate better health; however, these numbers are calculated through a general formula and should be taken with a grain of salt, as they do not factor in all individual variables nor provide insights into overall health status.

Are smart scales accurate?

While few studies have been conducted on the accuracy of smart scales, they are deemed less accurate than a DEXA scan.

For instance, one small study compared the results of 3 different commercially available smart scales and concluded that while they may accurately measure body weight, body composition metrics were off compared to those obtained from a DEXA scan.

Naturally, another question arises: what is a DEXA scan, and should you get it instead?

DEXA stands for dual x-ray absorptiometry and is used in clinical practice. While DEXA is primarily used for assessing bone health, it can also estimate body composition and is considered to be the gold standard. However, because it is only available in clinical settings, obtaining a DEXA scan is not as straightforward as stepping on an at-home smart scale.

While DEXA offers more accurate measurements, smart scales do have their advantages. Using a smart scale can be helpful if you want to track your progress. Our expert, registered dietitian nutritionist Leah Tsui, explained this approach in more detail:

Smart scales could be helpful when it comes to precision of measurement versus accuracy. Accuracy refers to how close a measurement is to the true or accepted value, so we would put DEXA scans as the gold standard here for accuracy. Precision refers to how close measurements of the same item are to each other, so if an individual uses a smart scale over time, they can compare their results using the same scale. It just may not be completely accurate.

Leah Tsui

However, day-to-day weight-ins may not be necessary as many factors may cause fluctuations, including hydration levels, meal timing, and foot placement. For menstruating individuals, as noted by Leah Tsui, the timing of your cycle can also affect the metrics. For tracking purposes, use your smart scale at the same time of day. Carefully read and follow the manufacturer's instructions, paying special attention to any specific foot placement guidelines provided.

Smart scales for weight management

When it comes to smart scales or any scales in general, one of the factors to consider is whether they are helpful for people on a weight loss journey.

Even if there are some accuracy concerns, studies do indicate that using a smart scale may contribute to better outcomes for those who are trying to lose weight. Consistent and frequent weight monitoring is linked to greater weight loss and improved maintenance afterward. This is most likely due to the increased self-awareness and further behavior changes based on the weight-in data.

In the weight management guidelines provided by the American College of Cardiology (ACC), the American Heart Association (AHA), and The Obesity Society (TOS), weight monitoring is also discussed alongside other behavioral changes. While it is essential for individuals attempting to lose weight to be in a caloric deficit, achieved by either reducing food intake or increasing physical activity levels, monitoring one’s progress is encouraged as an additional tool.

This does not imply that self-weighting is crucial for management or a general fitness routine. In fact, it may be harmful for some individuals. As noted in one literature review, frequent weight-ins could contribute to lower self-esteem, body dissatisfaction, and disordered eating, especially in younger people and women.

Should you get a smart scale?

I am still on the fence about whether smart scales are worth the investment.

I rarely use my smart scale. When I do, I don’t often check body metrics such as body fat percentage, visceral fat, or lean mass. For me, it brings too much stress. When I used it religiously, I noticed being overwhelmed by weight fluctuations (even the tiny ones), which, in my case, did not positively contribute to my fitness progress.

However, I can see how they can be helpful for those who want to track progress at home. Let’s face it, DEXA scan, although the gold standard, is not easily accessible. If tracking helps you stay on track (or allows you to see when adjustments are needed), a smart scale can serve its purpose.

Moreover, I personally find it great that smart scales force us to think about overall body composition — not just weight. Being stick thin should not be the ideal; lean mass is an important aspect of health. It took me years to break free from the societal ideals set for us and realize that smaller is not necessarily better, and if smart scales are contributing to the switch even a tiny bit for you, I am more than happy to see them becoming the new big thing.