We Tried 3 Fitness Trackers of the Future

Metabolic wearables do way more than track your steps, but are they really worth it? We put three to the test.

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August 17, 2022

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Photo by: Catherine Falls Commercial/Getty

Catherine Falls Commercial/Getty

Heart rate monitors to wear during exercise were a huge breakthrough in the late 1970s. Since then, we’ve developed multiple apps and trackers to monitor movement and food intake — and the devolvement of tools to monitor fitness, diet and exercise continues to evolve. The newest wave in health and fitness goes even deeper: New metabolic trackers are designed to measure your blood sugar, sweat composition and even the chemical compounds in your breath. As a certified athletic trainer and registered dietitian (RD) with over 20 years of experience working in the nutrition and fitness realms, I needed to know more. Are these gadgets the future of fitness or a total waste of money? Here’s what happened when I put three of the newest wearable metabolic technologies to the test.

What Are Metabolic Wearables?

Today, heart rate, oxygen saturation and calorie expenditure can be assessed on your wristwatch, and sleep can be tracked by a ring on your finger. Metabolic wearables track other aspects of your health including blood sugar, nutrient loss and macro-usage by analyzing your breath and sweat in addition to just sitting on your wrist.

Metabolic Trackers, Tested

What it does: Sweat analysis during exercise

How it works: From the makers of Gatorade, this one-use patch is worn during exercise to analyze the volume and composition of sweat. To use, you apply a self-adhesive patch to the forearm and scan it with the Gx app immediately after exercise. The app will recommend how much fluid and electrolyte replacement is needed.

Sweat testing is nothing new for sports medicine practitioners, but equipment and techniques can be expensive and difficult to interpret if you aren’t a healthcare provider. These patches are super-easy to apply, the app is user-friendly and, yes, the patches stayed on well through sweaty indoor and outdoor workouts.

Overall impression: While not as comprehensive as some more involved sweat testing, this is an awesome option for active folks to assess and optimize their hydration. A few sessions with it should be enough to determine your needs without breaking the bank.

Buy It
$199 to $350 per month, depending on the program

What it does: 24-hour glucose monitoring (for healthy people without diabetes)

How it works: Users take a comprehensive health questionnaire and are sent a wearable sensor just like the ones prescribed for diabetics. Sensors are attached to the upper arm (with little-to-no discomfort) and are paired with an app that logs all the data. You scan the sensor with your phone a few times a day for constant monitoring to see how sleep, exercise and diet influence blood sugar levels. The device can sync with your Apple watch to account for sleep and exercise. The subscription includes two (14-day) sensors per month. The cost is not covered by insurance, but is HSA and FSA eligible.

The program offers some guidance from a RD, but the app features several analytics that may be difficult for some to interpret. I did have a few issues getting my phone to properly scan the sensor and found conflicting info on whether or not you can swim with this device on (the manufacturer of the sensor indicated swimming was possible but Nutrisense advised against it). While it was interesting to see the data (and I was able to pat myself on the back to see nice blood glucose control), I’m not sure why healthy folks need this device in their lives.

Overall impression: Reliable technology but probably not worth the money for most healthy, active individuals

Buy It
6, 12, and 18 month “tracks” range in price from $249 to $349

What it does: Breath analysis to determine which nutrients are being metabolized to target personalized recommendations for diet and exercise

How it works: You breathe into a handheld device that communicates with an app. The gadget aims to be a more compact versions of metabolic testing machines that measure respiratory exchange ratio (RER). This ratio is derived by measuring the amount of oxygen being inhaled and carbon dioxide being expelled and translates that into data (a score of 1 to 5) that indicates whether you are “burning” fat (score of 1 or 2), carbs (score of 4 or 5) or both (score of 3) at any given time of day. Based on your readings the app modifies macronutrient recommendations, which seem to favor protein and fat intake well above carbs.

During my 2 weeks of usage, I always scored between 1 and 3, which indicated fat or fat and carb usage, yet the tailored carb recommendations the app prescribed were always lower than this active 40-something-year-old dietitian would want to see. This device can also be synched with an Apple watch to account for sleep and exercise; users are also expected to log food into the app. While intriguing, there is very little data to support the accuracy or effectiveness of this device. One small study funded by the manufacturer did report similar results to more comprehensive metabolic testing, although that type of analysis is not meant for daily use.

Overall impression: It’s an interesting concept but more research is needed. Some may find use of the device and app cumbersome (and possibly triggering) as you are expected to constantly assess your breath, enter meals and potentially modify food intake excessively. There also seems to be an underlying emphasis on restricting carbs.

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Dana Angelo White, MS, RD, ATC, is a registered dietitian, certified athletic trainer and owner of Dana White Nutrition, Inc., which specializes in culinary and sports nutrition. She is the author of four cookbooks First Bites: Superfoods for Babies and Toddlers, The Healthy Air Fryer Cookbook, The Healthy Instant Pot Cookbook and Healthy Quick and Easy Smoothies.

*This article was written and/or reviewed by an independent registered dietitian nutritionist.

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