The Withings Smart Body Analyzer is a smart scale that not only measures weight, but also calculates your body mass index (BMI) and fat mass, and registers heart rate and indoor air quality/air temperature. But at $150, it's on the high end of the market for a scale, even a smart one. So are the extra features worth the price? I tested the scale to find out.
The Smart Body Analyzer is a sleek-looking scale that's about 1 square foot (.1 square meters) in size, and fairly lightweight (a little over 4 lbs. or 1.8 kilograms). It has a rectangular display screen that lights up when you step on the scale, and the display is clearly readable. Once the scale has shown all your readings, the screen fades to black. You can press a silver circle in the center of the scale to check the indoor air quality and temperature. The device comes with batteries, so there's no need to charge it.
You can make profiles on this scale for up to eight people at a time, and the Smart Body Analyzer will recognize you based on your weight. It automatically takes readings every half hour of the carbon dioxide in the air and the temperature, and syncs with the Withings Health Mate app every 12 hours, or whenever you weigh yourself. Withings recommends that you keep the scale in your bedroom to monitor air quality where you sleep.
The Smart Body Analyzer is pretty easy to set up: Just pull a tab underneath the scale to activate it, and then hold down a button (also underneath the scale) to pair the device with your mobile phone via Bluetooth. Once you install and launch the Withings Health Mate app on your phone, the app walks you through how to use the scale.
When you step on the scale (with bare feet), the screen displays your weight, followed by your fat mass, your heart rate and the air quality/temperature measurement. It takes less than a minute to cycle through all these readings. A neat feature of the weight measurement is that small arrows appear on the four corners of the display screen, and tell you which way to move if you are not standing in a proper place on the scale for an accurate reading. Withings says you should balance your weight to make the arrows disappear — for example, if two arrows appear on the bottom of the screen, then shift your weight slightly forward.
The app keeps a record of all your measurements, as does the online account you create. For the most part, the device and app were easy to use, but I struggled to find explanations for what my weight measurements meant (e.g., how they compared to normal), or even what the term "fat mass" means. It turns out that Withings does provide these explanations, but they are a bit hidden. In the app, you need to select the Weight/BMI/Fat Mass section, then select the three dots at the top of the screen, and then select Help Center. This takes you to an FAQ section, with questions such as "What is normal weight?" and "What is body mass index?" All of the answers to these questions were quite useful, I just wish they were easier to find.
The scale also displays an arrow above a dark line on the fat mass measurement to indicate where your rating falls along the normal range, or if it falls outside of this range. But because this is not explained in the instructions, I actually completely missed this piece of information during my initial measurements. It wasn't until sometime later that I figured out what this line meant.
Value of information: ★★★☆☆
I found the scale's weight and BMI measurements quite accurate; I happened to visit the doctor a few weeks before I tried the Smart Body Analyzer, and my weight and BMI measurements on the device matched up pretty closely with what the doctor told me. However, my fat mass measurements were somewhat inconsistent, ranging from 6.5 percent to 9 percent in a single day, leading me to wonder how accurate this measurement was. (I assume my average measurement over time is more accurate than a single measurement.)
The FAQ section of the app not only does a good job of explaining the meaning behind the weight measurements, but it also suggests when to take measurements (in the morning, about 30 minutes after you wake up), and explains why some people go through weight fluctuations known as the "yo-yo effect."
The app and the online account also give you the option to display the "normal range" of weight/BMI on the same graph as your measurements, so you see how you compare.
The device monitors air quality by measuring carbon dioxide levels, and rating the levels as "good," "medium" or "bad." All of the measurements in my office were in the "good" range, about 400 to 800 parts per million (ppm). Other than this rating, there wasn't much explanation about the carbon dioxide readings on the app, but the Withings website says to "clear the air" (i.e., open a window), if levels are medium or bad. The website also says that very high levels of carbon dioxide, between 30,000 and 50,000 ppm, can cause nausea, headaches and breathing/pulse increases. I thought the company could have put more emphasis on the point that carbon dioxide is also a proxy for other pollutants in the air. That is, if you have a buildup of CO2, chances are other pollutants are building up, too.
The Smart Body Analyzer offers a few features to keep you motivated to step on the scale. In the Health Mate app, you can set a reminder to weigh yourself, and you'll get an alert at a scheduled time on your phone that reads, "Step on your scale now. When you weigh-in regularly you are more likely to achieve your weight goal."
You can also share your measurements by text, email or social networking sites, such as Twitter, which may be helpful for people who get an extra push from their friends.
Another device, the Fitbit Aria Wi-Fi Smart Scale ($129), offers some of the same features as the Withings Smart Body Analyzer, but the Fitbit's scale does not measure indoor air quality. So if air quality measurements are important to you, the Withings might be worth the extra $20. I personally did not get much value from learning about air quality; the numbers didn't change much for me and were always "good." But I tested the device in an office setting, and I could see how air quality readings could be more valuable in a home setting.
Conclusion: 13 out of 20 stars
If you're only interested in measuring your weight, you'll likely want to stick with a regular scale. But if you want a device that also measures your body composition and indoor air quality, then the Smart Body Analyzer may be right for you.
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Rachael is a Live Science contributor, and was a former channel editor and senior writer for Live Science between 2010 and 2022. She has a master's degree in journalism from New York University's Science, Health and Environmental Reporting Program. She also holds a B.S. in molecular biology and an M.S. in biology from the University of California, San Diego. Her work has appeared in Scienceline, The Washington Post and Scientific American.