While smart scales have been around for ages, body composition analysis is still a relatively new feature for wearable devices. For example, the Samsung Galaxy Watch 4 was the first smartwatch to natively include this feature. Amazon’s Halo Band was the first fitness tracker with this feature. The latter two were launched within the last two years. Meanwhile, Apple has yet to address body composition. For Apple Watch owners, you’ll need to look to accessories like the $149 Aura Strap 2.
Like smart scales, the Aura Strap 2 determines your body composition via bioelectrical impedance analysis (BIA). The BIA works by sending a weak electrical current through your body to calculate your body fat percentage, lean muscle mass, water, and sometimes niche measurements like bone mass. This particular strap measures fat, muscle, water, visceral fat (the dangerous type of fat), protein, lean mass, and minerals (an indicator of bone mass).
Compared to the company’s first version of the device, this one is 20% thinner and 5% narrower. The measurement process has also been simplified. Instead of taking three steps on the original Aura strap, all you have to do is touch the electrode on the strap with your palm and wait 30 seconds. Supposedly, these design changes allow Aura to record 16 times more data, and Aura Devices claims the second-generation strap provides around 95% accuracy compared to a DEXA scan – the gold standard. clinic to determine body composition.
It’s already a significant overhaul, but the Aura Strap 2 also changes the way you put it on. Instead of clasps, it now opts for a stretch band that resembles Apple’s Solo Loop band. It can be a pro or a con. If you use the Apple Watch primarily for health tracking, you probably already know how important fit is. Loose fits make measurements inaccurate, so you want the BIA sensor resting against your skin. This is more difficult to do with an elastic band. Out of the box, the Aura Strap 2 comes with the medium size strap pre-installed and three additional sizes in extra small, small and large. The medium strap did not fit my small bird wrists. Neither does the little one. Luckily the extra small did the trick – although I have friends with even smaller wrists than mine. If your wrist doesn’t quite fit any of the four straps, you’re out of luck because there’s no way to adjust the strap.
But while the extra little band fitted around my wrist, it was painful to stretch on my hands. I have larger than average hands and you can’t stretch the strap. (I can use an iPhone 12 Pro Max one-handed with no problem, and my fingers can stretch nine keys on a piano.) Luckily, the company says it’s safe in the shower and the pool, which means you don’t have to. remove it more than once a day. So while I normally take off my Series 7 to shower, you gotta let your wrists breathe, folks! — I kept it to avoid removing the bracelet. I also dreaded putting the strap on in the morning and taking it off at night. I admit this may be an issue specific to my body, but it is something to be aware of if you have large hands.
Another complaint related to the bracelet: to change bracelet size, you have to open the case that houses the battery and the electrode. What’s annoying is that you can’t just open it with your fingers. The strap comes with a little pick that you use to prop it up, but if you’re anything like me, you’ll probably lose it in seconds. But at least you can also use a credit card. It’s tedious if you have to try multiple bands to find your correct size, though it’s not a big deal beyond setup and when you need to replace the battery itself. Aura said the button cell battery should last about six months if you take just one reading a day. I can’t say if that’s true because I haven’t used the strap for so long. However, after about a week of testing with 2-3 tests per day, I’m left with about 76%.
Otherwise, the Aura Strap 2 is refreshingly simple to use. There are clear instructions on how to take measurements both in the iPhone app and on the watch itself. To take a measurement, simply place your palm against the electrode with the Aura app open on the watch. Aura recommends that you hold your arms in front of your chest – kind of like you’re about to do a Russian squat dance without the actual squat – but that’s it.
This is a huge step up from the Galaxy Watch 4. When I reviewed the BIA feature of this watch, Samsung gave me a long list of things I needed to check to get an accurate reading. This list included making sure I didn’t have my period or wear jewelry. It was annoying to use if you wore the watch on your right wrist, as you had to reach out to access the buttons. None of these issues were a problem with the Aura Strap 2. Although it recommended taking measurements around the same time each day, I didn’t have to worry about my period, my jewelry or the wrist I wore the Series 7 on, because Apple lets you customize the orientation of your watch.
My results were also consistent from reading to reading. They also roughly match the results I got on the Galaxy Watch 4 and the Amazon Halo View. However, unlike those devices, the Aura app gave me much better context on how those metrics relate to each other. All other devices told me I’m overweight or obese based on body fat percentage. Although body fat percentage is more useful than BMI, it is an incomplete picture. For example, my waist-to-hip ratio — another way of measuring your risk of heart disease based on your belly fat — is well within a normal range. Also, my smart scale usually puts me between 27-31% body fat. Basically, you should always keep in mind that these devices can help you measure progress, but they may not be accurate when it comes to your specific health condition.
That’s why I was impressed when the Aura app said that even though my body fat percentage was slightly higher than normal, I had a “good balance of fat and muscle.” Typically, you don’t get much more than simple numbers with body composition features. I also liked how the app described each metric and how I should interpret it. For example, my visceral fat percentage was 1%. Normally, I think that’s a great thing. However, the app noted that having less than normal visceral fat could indicate that I didn’t have enough for my body needs and to check with my doctor if my visceral fat was out of range for an extended period of time. He also explained that the “norm” was based on the general population and did not necessarily take into account my individual metabolism, lifestyle choices, or personal standards.
If you have a specific body goal – whether it’s to lose weight or get picked up – the Aura app will also contextualize where you are and how to get there. I set myself the goal of an “athletic” body with muscle mass gain. The app, in turn, told me I was about 80% of the way there already and recommended that I increase my calorie intake by 10-15%, add more protein to my diet, and not to do more than three workouts per week.
The best part is that weight is not a big focus of this app. You have to grab it initially, but even if you set yourself the goal of losing fat, it never recommends that you “lose weight”. Instead, he recommends that you reduce your intake of carbohydrates and sweets for two weeks and exercise.
But while I appreciated the additional analysis and context, I didn’t like that much of it was locked behind a paywall. If you want monthly fitness and nutrition reports, guided workouts, or an upcoming feature that lets you chat with a personal trainer, you have to pay $9.99 per month or $79.99 per year. I can’t say for sure if the extra cost is worth it, as I tested a pre-launch version of the app. The library of workouts I had access to was simple and easy to follow, but limited to one workout per body zone and skill level (beginner, intermediate, advanced). Also, I haven’t had the full experience of the monthly report as I’ve only been testing for a few weeks. You’re already spending $150 on an accessory. Adding a subscription makes business sense, but it’s yet another thing to pay for. And people who would be inclined to buy this device probably already pay for several fitness-related subscriptions.
In the end, I was pleasantly surprised by the Aura Strap 2. It’s not perfect, but again, few accessible body composition gadgets are. What sets it apart is a better app that offers holistic information and context. It’s certainly a niche product, but what if you’re an Apple Watch owner and want to change your body composition? You could do much worse.
Photography by Victoria Song / The Verge