Should You Wear a Fitness Tracker?

Should You Track Your Fitness in-lineFor a nation of supposedly obese, lazy, and sedentary layabouts, American consumers sure are interested in tracking their daily activity levels. In 2015, they bought 13.4 million dedicated activity trackers, up 50% from the previous year, and spent almost $1.5 billion on the devices. That’s in addition to the hundreds of millions of smartphones in circulation that also track your daily steps, sleep quality and duration, and calorie expenditure. From FitBit to Jawbone to Apple Watch to dozens of others, the wearable fitness-tracking gadget industry is growing quickly. Venture capital has responded, pouring billions into the wearable industry.

Are they worth it?

It depends. According to some data, about a third of users stop using their devices within six months of getting them. Then again, “most people” don’t know the difference between polyunsaturated and saturated fat. “Most people” don’t care enough to watch their carb intake, or pay a little extra for grass-fed beef, or eat a Big Ass Salad every day. These statistics collate yet ignore individual data points. If you decided to pick up a FitBit or a Jawbone or an Apple Watch, the only data point that matters is yours. Most people might stop using their wearable after a couple months. You might keep wearing it.

Are they accurate?

According to research from December of last year, they aren’t very accurate at tracking data beyond step count. Researchers analyzed 22 studies exploring the ability of FitBit and Jawbone (the two most popular trackers) to accurately track, sleep, steps, calories burned, distance, and physical activity. They were both good at counting steps, but missed the boat on almost everything else.

They overestimated sleep duration. Overall, accelerometer-based sleep-tracking wearables compared poorly to established medical devices for tracking sleep, like polysomnography (used in sleep studies) and actigraphs.

They underestimated distance traveled at high speeds and overestimated distance traveled at low speeds.

One study found that the FitBit accelerometer was fairly accurate when assessing physical activity; others found that both the Fitbit’s and the Jawbone’s were not.

Both tracker brands underestimated and overestimated calories burnt, depending on the study.

A 2016 study looked at four different brands—FitBit Charge HR, Apple Watch, Mio Alpha, and Samsung Gear S—of wrist trackers and found that while heart rate tracking was accurate, energy expenditure tracking was not.

Another 2016 study found that while most trackers are accurate with step tracking over flat ground, step tracking on stairs is less accurate, and distance tracking on stairs is overestimated by at least 45%.

That said, these aren’t huge hits against wearables. Raw step count and resting HR are the most important features of today’s fitness trackers, as they allow you to track:

Daily activity. Are you moving frequently at a slow pace? Are you hitting the 10k step mark? Walking is the foundation of good physical, mental, and psychological health. It’s fundamental to our species—we’re walkers.

Heart rate zone. If you’re at all interested in becoming a fat-burning beast, spending a lot of time in the aerobic heart rate zone (180 minus age) will get you there, and a HR monitor can help you figure out what it looks and feels like.

The million dollar question: do they encourage more activity?

Surprisingly, few researchers have even explored this fundamental question: whether fitness trackers increase activity. What exists isn’t very encouraging.

A 2015 study gave overweight middle aged women either a standard pedometer (counts steps and distance) or a wearable fitness tracker. Both groups were coached to take 10,000 steps a day and engage in moderate aerobic activity for 150 minutes a week. After four weeks, the pedometer group saw no improvement. The fitness tracker group was little better, only increasing weekly activity by 38 minutes. No one reached 10,000 steps a day.

Anecdotes of how wearing a tracker changed this person’s fitness and helped them lose a dozen pounds and lose that baby weight abound, and I’m hesitant to discount them. If tracking your activity really does encourage you, then it works. For you. And since this thing we call society consists of millions of subjective realities traipsing about, each crafting a separate narrative, “for you” is the only relevant qualifier.

Okay, all that aside, most of the downsides I’ve discussed derive from limitations of the technology. Wearables are still young. Future tech will improve, and I’m confident that within 5-10 years we’ll have consumer-level devices that accurately track sleep, calorie expenditure, metabolic rate, fat-vs-sugar-burning ratio, and dozens of other biomarkers. It’s only a matter of time.

But there’s another potential downside, one that has little to do with the accuracy of the technology or the technology itself. It’s how we silly humans exalt numbers over feelings, objectivity over subjectivity.

This has its advantages. When we can track it, people who otherwise might not put in the effort suddenly care about getting enough steps each day. Put something down on paper/in an app and it becomes real. You care more about what you can quantify. You pay closer attention to your steps per day, and aim for more each day, when you’re getting real time feedback, your friends are getting notifications when you hit your goals, your wrist is buzzing with excitement over your 10,000th step. When you’re wearing a fitness tracker, getting 10,000 steps doesn’t just make you healthier, it makes you happier. And health-seeking behaviors only become second-nature when we can derive intrinsic value—happiness, in this case—from their pursuit.

This all sounds great, Sisson. What’s the downside?

Once you start quantifying your physical activity, activity you don’t track loses value.

If you forget your wearable, you lose your steps. If your exercise session won’t show up on your daily wrap-up, if, God forbid, your FitBit friends won’t see all the walking you did today, you may be less likely to do it. Especially if you’re only walking to pad your stats.

It’s like the tree falling in the forest. Did you really take that walk to the grocery store if your FitBit wasn’t there to record the steps? Did you actually reach the fat-burning aerobic zone in your long easy run if you forgot to wear the heart rate monitor?

Are you walking so much because you like the small hit of dopamine that floods your brain every time you get another thousand, or do you actually enjoy ambling around? Is your motivation truly intrinsic?

Before the trackers, steps taken were lost to the past. You’d step, and shift your weight, and it was over. Gone. You might recall where you walked and what you saw and whom you were with, but you didn’t have any real notion of how many steps you’d taken. The thought to count them never even entered your mind. You could, but it’d be laborious and frankly ridiculous to count your steps in your head.

You know. You know now. But your FitBit friends don’t. And before long—a week or two, maybe—you’ll have forgotten all about it. If that scares you, there may be a problem.

Maybe I’m old school. Maybe I don’t get it. Maybe I’m a Luddite (who just so happens to run a successful online business). But I’m far more interested in fine-tuning my intuition than relying on technology to tell me how healthy I’m being. I’m not saying you shouldn’t use them.

If you want to use one, just do it right:

Wear it on the same spot. You can wear it on your lapel, your hip, your wrist, or your ankle as long as you wear it there every time. The more consistent you are, the more accurate the device will be.

Be accurate when entering your personal data. To give you accurate data, the tracker needs to know your real height and weight. If your weight changes, update it.

Calibrate your step length. Some wearables allow you to calibrate your true step length when you start using the device. Doing so will improve the accuracy of distance tracking.

Stop moving when taking your heart rate. Most consumer wrist-wearables are unable to accurately track heart rate when you’re in motion. To get an accurate reading, stop exercising and rest for 5-10 seconds before checking your HR.

Focus on trends, not absolute numbers. If what the device says about last night’s sleep corresponds to how you feel about last night’s sleep, it has value. If it conflicts—if you feel great despite getting poor marks on your tracker—it’s probably inaccurate. But that makes you wonder: if you’re only using the tracker to confirm your subjective impressions, how valuable is the tracker? Just use your intuition.

Remind yourself every morning that you are a privileged rich person who’s probably already rail-thin. The added weight of your guilt will increase your heart rate and calories burned.

Most importantly, use your fitness tracker to enhance and inform your intuition, not replace it.

This wasn’t intended to be a review of all the available fitness trackers. It was a quick review of the evidence for and against along with my personal take on the technology.

I’d love to hear about your experiences with wearables down below. What worked? What didn’t? What did you gain from wearing a fitness tracker? What have you lost?

Thanks for reading, everyone.

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About the Author

Mark Sisson is the founder of Mark’s Daily Apple, godfather to the Primal food and lifestyle movement, and the New York Times bestselling author of The Keto Reset Diet. His latest book is Keto for Life, where he discusses how he combines the keto diet with a Primal lifestyle for optimal health and longevity. Mark is the author of numerous other books as well, including The Primal Blueprint, which was credited with turbocharging the growth of the primal/paleo movement back in 2009. After spending three decades researching and educating folks on why food is the key component to achieving and maintaining optimal wellness, Mark launched Primal Kitchen, a real-food company that creates Primal/paleo, keto, and Whole30-friendly kitchen staples.

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