健康手环真的有效吗？

健康手环真的有效吗？

可穿戴设备在越来越广泛地被人们应用在健康领域，但是该设备是否真的有助于减肥，科学家们进行了科学实验。

测试中可能遇到的词汇和知识：

seraph六翼天使['serəf]

bracelet手镯[ˈbreɪslət]

chide责骂[tʃaɪd]

pedestrianism徒步[pi'destriənizəm]

compensatory补偿性的[kɒmpen'seɪtərɪ]

Are fitness trackers effective?（884 words）

By Anjana Ahuja

The devil on the shoulder has been replaced by a digital angel on the wrist — for many of us,at least. This seraph,perhaps a Fitbit bracelet or an Apple Watch,chides us silently to get off the bus a little earlier,take the stairs instead of the lift,and thus achieve the hallowed target of 10,000 steps a day.

Such keen pedestrianism,promise makers of wearable activity trackers,is the key to becoming fitter and,it is implicitly suggested,slimmer.

Except that the emerging evidence does not quite match up to the marketing pitch. A study conducted by the University of Pittsburgh measured whether fitness devices aided weight loss and found people shifted more flab when they were not wearing trackers.

The scientists are not quite sure why but it might be that fitness devices double up as both angel and devil,spurring the wearer to climb the stairs and delivering information on calories burnt — leading to a compensatory cookie on the top floor.

Around 470 overweight adults enrolled on the Pittsburgh trial. All were told to diet and exercise more,which is standard advice. Six months in,half the participants were randomly assigned to an“enhanced”intervention: they got a fitness tracker,could monitor their progress and receive feedback through a website. The expectation,according to Professor John Jakicic,who led the study,was that the bells-and-whistles group would shed the most weight.

The results,collated two years after the experiment started,confounded expectations: the unmonitored slimmers lost an average of 5.9kg,whereas their digitally tracked peers shed 3.5kg. In September the authors concluded in the Journal of the American Medical Association that“devices that monitor and provide feedback on physical activity may not offer an advantage over standard behavioural weight loss approaches”.

It is a lovely piece of research,because it actually bothered to measure something that most of us had taken on trust: that activity trackers help us to better execute good intentions. Indeed,wearable health technology has become a profitable juggernaut: one market research company forecasts that,worldwide,53m fitness trackers will be sold in 2016.

And yet the evidence on their effectiveness has struggled to keep pace with consumer enthusiasm. One issue is the algorithms used to count steps and estimate the number of calories expended. These vary between devices,as shown by guinea pigs who have worn several trackers simultaneously.

One tester found that,over a week,her tally of calories burnt,as measured by Jawbone and Fitbit devices,differed by more than 2,600. That’s roughly a day’s worth of eating. If you have a tracker that systematically over-counts the calories used up,and you dine accordingly,you are unlikely to lose weight.

The companies claim the discrepancies between trackers are down to different algorithms and different sensors. As a very general rule of thumb,the more sensors a tracker contains — accelerometers for detecting motion,and altimeters and gyroscopes for orientation are standard — the more accurate it should be about the nature,frequency,intensity and duration of your activity.

For example,some trackers contain sensors that shine light on to the skin and,by looking at the light reflected from blood vessels,work out how energetically the heart is pumping.

Device makers,perhaps aware that comparison tests undermine the scientific validity of their products,point out that it is the trend in activity that wearers should focus on,rather than precise data. In that respect,fitness devices might prompt people to become more active.

On the other hand,fitness is not the same as weight loss. Shedding a spare tyre is a matter of dietary arithmetic: if you eat fewer calories than you expend,you will lose weight.

The unexpected outcome of the Pittsburgh study could,Professor Jakicic has theorised,be down to users setting too much store by the technology,and losing sight of the advice to which all overweight people should adhere to: eat less and move more. Fitness devices tend to address only one half of that mantra. The technology has moved on since the Pittsburgh guinea pigs first enrolled,but,before buying a tracker,it is still worth considering carefully how it will help you to achieve your goals. Be honest: do you want a calorie counter just so you can tell when you have earned the right to a cupcake? Or is your fitness bracelet a lifestyle statement?

As someone who does not wear a tracker — I fear that in technology terms I would be categorised as a late-to-never adopter — there is something rather pleasing about modern science confirming the value of an old-fashioned approach to keeping fit and staying trim.

Fortunately my domestic routine includes about 90 minutes of daily walking（through necessity,not virtue). I try not to eat too many cakes,or drink too much wine. I no longer own bathroom scales; the zips on my dresses and a full-length mirror offer unforgiving feedback. The low-tech approach is deliberate: I already spend too much time checking emails and social media accounts,and to fret over steps and calorie expenditure would be a digital fixation too far.

In any case,how have we become obsessed with reaching 10,000 steps a day? This figure is so perfectly rounded that it invites closer inspection — but that is a discussion for another day.