Fitness tracker calorie measurements not all that accurate

[doogald]

A recent study shows that fitness trackers with integrated heart monitors, including the Apple Watch, are pretty accurate, but that energy expenditure - the red ring on the activity app of the Apple Watch - are not so reliable. The Apple Watch is better than some other devices, but still is off by as much as 25%-50% in either direction (fewer calories recorded or too many.)

See https://www.theguardian.com/technol...f-step-when-measuring-calories-research-shows or, if you really want to geek out, the actual study at JPM | Free Full-Text | Accuracy in Wrist-Worn, Sensor-Based Measurements of Heart Rate and Energy Expenditure in a Diverse Cohort | HTML

To be honest, since the watch is measuring activity the same way every day, it's probably a relatively reliable way of tracking one day to the next, but people may want to rethink caloric food intake based on the activity reported by the health app.

 

[rangerdeyo]

I just saw this article and was impressed at how accurate the original Apple watch was at measuring heart rate (2% error rate) but disappointed overall at how all of the trackers were at measuring energy expended.

But if you wear it every day, you at least get a baseline on how your day to day activity looks.

 

[cwbcpa]

None of these devices are going to be accurate in measuring energy expended. They are meant to provide day to day data for comparison. If I sit on my butt one day and my watch says I burned 300 calories and then the next day I lift weights and also run for 20 minutes and the watch says I burned 800 calories obviously that is better. Where the real benefit comes into play is when you workout daily and you push yourself to increase that calories burned number week over week. It doesn't matter that it's not 100% accurate. It matters that I continue to push myself to do more. That becomes more of a challenge as you get into better shape.

It's the same with a scale. It's just a tool. You should not be relying on it alone either, if at all.

 

[doogald]

The concern about with energy expenditure is that the AW is off by 25-50% in one direction while you are active/working out but off by 25-50% the other way while you are relatively idle, just as an example. Or that somebody cross-training cannot accurately measure one activity to the next based on reported active calories. In that case, even a day to day comparison could be not that useful. The study seems to be saying that heart rate measurements may not correlate as well between activities as the fitness trackers would like.

<soapbox>Of course I am not a huge fan of the complete the rings mindset - especially the stand one, which will advise me at 10 minutes before the hour that I should take the time to stand while I've been standing for the past twenty minutes (this has happened more than once), or that rewards standing for 5 minutes an hour for 12 hours more than somebody who stands for an aggregate 3 hours in a 4 hour period but less than 5 minutes an hour for the next eight hours. It's not the smartest measurement in my opinion. At the same time, if I exceed the move ring by more than 50% for six days in a week but just barely do not reach it on a seventh day when I take a rest day, it seems like that should still get credit for seven days of movement as somebody who barely exceeds the move ring for all seven days. After all, rest days are an important part of training, and it's better to take a rest day rather than overtrain into an injury that forces many days of inactivity.</soapbox>

 

[Mac Guy]

The rings are for the 90% of the people that are Apple's iDevice demographic.

I don't know if there are portable medical grade devices that are highly accurate, and if so, what they'd cost. It would be nice if they all met some established accuracy standard.

No matter what brand/model tracker you use, accuracy isn't all that critical if the device is reliable and consistent in it's performance. If it's alway the same 5/10/2-5/50% accurate, you have that aforementioned baseline or yardstick even if you're not sure how long that yardstick is.

That can make comparisons difficult and bragging rights specious, if that kind of thing is important.