Calorie count query.

[Chris1963]

As much as the HRM accuracy concerns me I can still use a chest strap when I want to.

Calorie count I can't as it's an all day thing. I've long thought the Surge over counted.

I just took a short walk this evening along the river (no elevation involved) .

I ran GPS on the outward and coming back went to auto and I jotted down the numbers.

What does anyone make of this?

Steps :  Outward GPS mode 2463  Return Auto 2422   pretty good, less than 2% out accounted for by natural meandering. ( I know GPS v Tracked doesnt alter step count, I was just interested in comparing )

Distance : GPS 1.27 miles  Auto 1.14  Hmmm, 0.13 or around 230 yards out. I must adjust my stride length.

Calories : GPS  189 calories   Auto  206.  So 148 per mile against 162.  Jeez, I reckon at 53yrs, 190lb and 6ft I should clock about 90/100 calories per mile . No wonder the weight isnt coming off as quick as I'd hoped !!

That aside why would the two numbers be different? Is it down to the stride inaccuracy? How do fitbit use to calculate calories? And why would there be two quite different numbers?

I'm more concerned at the 148/162 figure per mile though - any ideas? It makes it pretty useless as a calorie counter as well if its recording 50% more burned than I actually do.  Oh HR was around 100 average, but of course registered 90 on return ( which gave the higher calorie burn!)    

Any thoughts?

[RobertoME]

Hello @Chris1963, good to see you around in our community. I was reading your post and I have some questions. I wonder what you mean when you refer to Auto? Are you using beside the GPS other feature of your Surge? 

As far my knowledge goes, the calories are burned considering your demographic information like gender, age and so on. Along with the amount of steps you do in a period of time and the intensity you maintain during this period of the exercise. By consequence you will have active minutes and as more minutes you have, more calories you will burned. Even if the activity is the same, because the tracker detects subtle differences in exertion that may explain why two seemingly identical activities result in different numbers. Also as you know half of your calories include your BMR too.

However as I mentioned, I would like to know what you are using to compare your numbers?

If you are so kind in letting me know this details I'm missing, I will be able to offer you a better explanation or help on this. 

I'll be around and hope to hear from you soon.

[Chris1963]

Hi.
Surge has two the modes, GPS walking and the one that auto recognises walking activity - Smart track. These are the two that were used that recorded the two different calorie counts. Confusingly the walk that recorded the lower heartrate showed a higher calorie burn.
I'm aware of BMR etc.
As I mentioned the steps were accurate, I've adjusted my stride length to get a more accurate distance when not in GPS.
What interests me though is the calorie count difference between GPS and smart track, and the HR difference. Same walk, same steps. Calorie counts 148 per mile on GPS and 162 per mile with smart track.
That discrepancy aside both readings seem very high for walking a mile. I expected around 100
per mile.

[Chris1963]

I should add as I mentioned in my original post, the HR in Smart track was lower than that using GPS by 13 bpm (same walk, same time, no elevation) but Smart Track recorded a higher calorie burn...!

Surely I should expect an almost identical calorie burn and HR when the walks are identical, it is done within minutes of the other, there is no elevation, for all purposes the same. And yet HR is different and calories per mile are different, and seemingly very high.  

[RobertoME]

Hello @Chris1963, thank you for letting me know more details. Note that I'm not able to see your information, so I replicate your scenario. Of course it wont be the same result due to the different demographic data. Although it gave me the same results as you explained here. The calories with Smart Track where higher in comparison to the GPS activity. So here are my comments and it has to do with my previous attempt to explain this. 

My activity with GPS was a walk from my home to the supermarket with a time duration of 46:45 min with 2.55 km. and 101 bpm which gave me 325 calories. Now here is where I found the difference in the calories vs the activity with SmartTrack. With Active minutes using GPS I got 42 minutes. With SmartTrack the same as you, the steps and heart rate were the same, only for a few minutes of duration of difference in the activity, but my active minutes were higher with 46 minutes. Giving a difference in calories with 336 calories. Here is where it comes my previous explanation in play. This difference is based on your speed and exertion levels (e.g. out of breath vs not out of breath, etc) will cause different active minute totals for the two activities and therefore the calories will be different. Also keep in mind with SmartTrack there is no pace information due to the lack of GPS, so with GPS the walking activity it would be slightly more accurate due to the inclusion of Pace.

So if you look your activities on your account you should be able to see different active minutes which will explain the different calories count.

Hope this helps and see you around.

[Chris1963]

Hi Roberto, thanks for your input, I understand your points...I probably wasn't clear enough as I rambled on. My main concern is the level of calories counted as being burned  - do you think it is really the case that it is 150-160 per mile? Everywhere I look on the net suggests around 100 per mile at a normal pace?  

[AlvaroFitbit]

@Chris1963 Remember that the calorie calculations are based on your BMR and the activity you are performing but are intended as a guide not an extremely accurate reading. Another thing you can do is use an alternative app/website and allow it to sync your exercise information with your account. This way you will have a calorie calculation that you will find more appropriate. You can find several great apps that can sync with your Fitbit account here.

I'll be around!