Can Apple Watch get you in shape? Here’s what the science says.


Does the Apple Watch activity app have all the answers?
Does the Apple Watch activity app have all the answers?
Photo: Graham Bower/Cult of Mac

If you’ve considering buying a shiny new Apple Watch Series 2, you might be wondering if it can really help you to get in shape. Especially if you’ve seen the recent headlines claiming that fitness trackers don’t work.

So what does science really have to say about wearables? I decided to investigate the science behind Apple Watch fitness assumptions.

What a good fitness tracker does

There are two key functions for an effective fitness tracker. First, it must tell you to do the right things. Second, it should persuade you to follow that advice. After all, the best fitness advice in the world is still useless if you don’t follow it.

So does Apple Watch deliver? Let’s look at the evidence.

Is Apple Watch fitness advice good?

Apple Watch makes three recommendations for your wellbeing: Sit less, move more and get some exercise. That’s what the Stand, Move and Exercise rings in Apple’s Activity app are designed to track.

But Cupertino makes no promises as to the benefits you will get from following this advice. The Apple Watch website used to cautiously say that it helped you to “live a better day.” But even that nebulous claim has now been erased.

Is there really any evidence that achieving these three goals will improve your health?

I asked that question to Cardiogram CEO Brandon Ballinger, who has amassed plenty of data on whether Apple Watch owners have healthy tickers.

Ballinger and his team recently conducted a study analyzing the resting heart rate of 6,668 participants who use the Cardiogram app. Your resting heart rate is a measurement of how fast your heart is beating when you are resting and relaxed — like when you have just woken up in the morning.

Why did they look at resting heart rate? The Mayo Clinic says “generally, a lower heart rate at rest implies more efficient heart function and better cardiovascular fitness.” Which sounds like a good thing. So if the Activity ring goals are improving the fitness of Apple Watch users, you would expect to see a lower resting heart rate among those who are completing their rings. And the good news is, that’s exactly what Ballinger’s team found.

Activity ring goals compared with resting heart rates
Activity ring goals compared with resting heart rates.
Photo: Cardiogram

As you can see from the chart above, test participants who clocked more minutes of exercise on the green ring, and calories on the red ring, tended to have lower resting heart rates. Ballinger says “on average, each 18 minutes of exercise translated into a 1 bpm decrease in resting heart rate. Equivalently, 178 calories of movement per day translates into a 1 bpm decrease.”

This does not prove that the relationship is “causal.” Just because the data show that people who do more exercise on average have lower resting heart rates, that does not prove that using the Apple Watch helped. Maybe they were more active because they already were fit and therefore had lower resting heart rates, for example.

And even if it is true that you can lower your resting heart rate by using the Activity app, that’s only a means to an end. Scientists call this a surrogate outcome. What really matters is whether you get a significant health benefit — like not suddenly dying. Since this kind of outcome is fortunately quite rare, and it will hopefully take decades before we know how long we will live, right now the truth is we don’t know if Apple Watch users enjoy longer, healthier lives. Which may explain the absence of extravagant health claims in Apple’s marketing.

What do scientists recommend?

Ballinger’s research suggests that Apple’s three goals may help you reduce your resting heart rate. But are these goals the best advice you can get, and is there any other activity you should be doing to improve your health? To answer this, I compared the Activity goals with the World Health Organization’s recommended levels of physical activity for adults aged 18 to 64, which are:

  • Do at least 150 minutes of moderate-intensity aerobic physical activity, or 75 minutes at vigorous intensity, every week.
  • This activity should be sustained in sessions of at least 10 minutes’ duration.
  • You’ll get even more health benefit if you increase the duration of your activity (to 300 minutes per week for moderate or 150 per week for intense).
  • Do strength training (e.g. weightlifting) at least twice a week.

The first three points are similar to Apple’s Move and Exercise goals. But the forth point is not covered by the Activity app at all. So if you are serious about being more active to improve your health, in addition to completing your Activity rings you should also get down to your local gym and lift some weights.

What about the stand goal?

The World Health Organization does not include standing in its physical activity recommendations, but it does highlight the dangers of a sedentary lifestyle, arguing that a lack of exercise “could very well be among the 10 leading causes of death and disability in the world.”

The evidence seems pretty clear that we can benefit from sitting less. But is standing up for just a couple of minutes every hour for 12 hours, as Apple recommends, sufficient to protect yourself from the health risks of an otherwise sedentary lifestyle? Once again, I can’t find any evidence on this one way or the other, but standing once an hour is presumably better than nothing.

Can Apple Watch help you stick to it?

apple watch heart rate sensor
Will Apple Watch fitness data get you to exercise?
Photo: Ste Smith/Cult of Mac

In scientific jargon, the Activity app is a “behavioral change intervention.” It is not just supposed to tell you what to do, it is actually intended to help you change your behavior. Forever. And that is a pretty tall order. Especially since we have a tendency to get stuck in our ways, following well-worn routines.

Changing habits is possible, but not easy – there have been many books written on the subject. Can a tiny gadget you wear on your wrist really succeed where so many experts have failed?

Not according to research published recently by University of Pittsburgh which found that “the addition of a wearable technology device to a standard behavioral intervention resulted in less weight loss over 24 months.”

This research got loads of media coverage, with shock headlines like: “Sorry, your fitness tracker is probably useless” and “Fitness trackers can backfire when it comes to weight loss.”

The trouble with these sweeping conclusions is that there are many different brands and models of fitness tracker, and they all do slightly different things in different ways. It’s crazy to assume that just because one tracker does not work that none of them do. The gadget used in the research was the Fit Core by BodyMedia, which has since been discontinued. (That in itself does not say good things about the device’s effectiveness.)

Had the researchers used an Apple Watch, maybe the results would have been different. Maybe. The truth is, we just don’t know, because the research does not yet exist.

Once again, science draws a blank.

‘My grandmother smoked her entire life and lived to 100’

While science can’t yet tell us if Apple Watch works, there is no shortage of people sharing stories of their success in using the gadget. Apple commentator Jim Dalrymple famously lost 40 pounds thanks to his Apple Watch. And last year I wrote about seven Cult of Mac readers who achieved similar success.

The trouble is, by cherry-picking anecdotal evidence in this way, you can pretty much prove anything. If I found a bunch of people who had played Russian roulette with a loaded gun and survived to tell the tale, would you take that as evidence that it was safe? You might quite rightly say, “Yeah, but what about the other guys that found the bullet?”

You hear plenty of stories from people who know someone who smoked their entire life and still lived to an old age. This proves nothing. It is no good just looking for evidence that supports your argument. You need to look at all the evidence, whether you like it or not. This includes testing what scientists call “the null hypothesis” — the possibility that the effect you are looking for does not exist.

If you really want to know if Apple Watch helps people get in shape, you need to define precisely what you mean by “in shape.” Then you must perform a “randomized controlled trial”, in which test participants get randomly assigned to two groups — one with and one without Apple Watches — and see which group finds the most success. Until this kind of research is conducted, we just don’t know for sure.

Hey Siri, wake me when I’m fit

If all this is starting to sound a bit wishy-washy, then good. Because the truth is that available science just can’t tell you if an Apple Watch will help you get in shape. Ultimately, that’s down to you. You certainly can’t expect to sit back, relax and let your Apple Watch do all the work — “Hey Siri, wake me when I’m fit.” It just doesn’t work that way.

Asking if fitness trackers work is the wrong question, in my opinion. It’s like asking if a knife and fork will feed you. Of course not. But if you use them properly, they can help you eat. In the same way, if you use your Apple Watch properly, it can help you to get in shape.

To find out how, check out our free ebook: Cult of Mac Fitness Handbook: How to Get in Shape With iPhone and Apple Watch.

Cult of Mac Fitness Handbook


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