24/7 HR Sampling

Both I would imagine.

Does the Fitbit include BMR calories would you know? That's a common reason for calories being much higher.

From the Fitbit website:



How does Fitbit estimate how many calories I've burned?

Your basal metabolic rate (BMR) is the rate at which you burn calories at rest just to maintain vital body functions like breathing, heartbeat, and brain activity. Your BMR usually accounts for at least half of the calories you burn in a day and is estimated based on the physical data you entered when you set up your account: gender, age, height, and weight.

The calorie burn estimate that Fitbit provides takes into account your BMR, the activity recorded by your tracker, and any activities you log manually.

Your tracker's calorie count will reset each night at midnight and begin counting immediately thereafter. BMR is the reason your tracker starts the day with calories already burned—you've still burned calories even if you haven't gotten out of bed yet.

On the rare day I do very little it seems about right. I.e. 2400 - 2500 calories burnt in the day. Any activities are imported into Fitbit and overwrites the data recorded. So I'm happy with that. The discrepancy seems to be when doing general activities with add steps and increase HR and this seems to be where I am getting a difference. The Fitbit is definitely over counting steps when doing activities which involve arm movements (washing the car, washing up). The Garmin is apparently not counting steps less than 10 to avoid false counting and therefore possibly over counting. Low sampling rate on HR for the Garmin may be a factor if it misses HR spikes but I have had it on broadcast mode for a lot of the day and the Garmin is still 700 calories down compared to the Fitbit. So I'm not sure what to believe :-(

It may also have something to do with what your FR235 has set as your BMR. I don't know how either Fitbit or Garmin calculates this. I've used 3 different online BMR calculators and mine averages out to 1803. Now that I've figured out how to view my fit files, I've discovered my FR235 has mine set to 2085. Same information, but nearly 300 higher than the others. I can't find any info on why this is. Since the FR235 isn't taking heart rate readings 24/7, it's "predicting" how many calories I should have burned throughout the day outside of doing a workout activity (active calories) based on that number.

So just to clarify, this means that the Garmin is effectively adding 300 calories to your 24rh burn reading?

Yes, I believe so. I guess it's easier to explain it this way, because I've actually done this. Calories burned are reset at midnight. I have taken my watch off and set it on the nightstand while it's still turned on. I wake up at 5 AM. The watch will say that I've already burned around 400 calories even though I wasn't wearing it or no activity was performed. It's taking into account based on sex, age, weight, height, etc. this is how many calories I burned (MBR) in that 5 hr window. This is fine. The problem is, Garmin set my MHR to 2085 when it's actually around 1800, so the 400 calories burned wouldn't be accurate. I don't know how Garmin came up with 2085, nor can I figure out how/if I can change it. The only thing that I can think of that might cause this is the active level setting. I have mine set at 6. Maybe Garmin is figuring that at that level I'd burn an additional 300 calories than normal? I'm going to change that level to a 2, check the fit file again and see if that's making a difference.

My watch calculates BMR at about 2200 whereas every other online calculator I have tried gives a value between 1900-2000.

the BMR does not include all the calories burned outside of steps and monitored activities like runs etc. Therefore your estimated burn to digest food, sit at a computer etc etc is estimated and added on. I believe the activity class set under user settings on the GC app helps to set that. I doubt that the 24/7 HR monitor has anything to do with calorie burn other than when used in an activity....(otherwise it would have been stated specifically as a shortcoming for the FR230 and FR630). I don't think the fitbit says any different.

The difference between calories in my activities and daily steps and the overall total seems to be a consistent 2049 calories. At 49, male, 73kg, 195cm tall "online calculators" typically put my "BMR" at about 1700 calories.

I don't think that my 2049 is necessarily strictly BMR.

For instance, these online calculators often don't tend to ask how active you are. My activity class in Garmin Connect is set to 8 (7-11 hours of almost daily exercise) which is about right most weeks. I suspect then that some of the difference between the two numbers above can be attributed to the activity class. The other difference is probably solely because Firstbeat do the calories for Garmin but online calculators often use Mifflin - St. Jeor equations (see also https://en.wikipedia.org/wiki/Basal_metabolic_rate ) and different algorithms will come up with different numbers.

It is also fairly apparent the online calculators use a generic calculation method (say like 220-Age for max HR) and so everybody's actual BMR will vary with other things like body fat percentage in a similar way to the fact that 220-Age for max HR does not work that well for a lot of people.

I read through the thread because personal I'm sad about 24/7 HR tracking and from this calculated calories burned over the day. I'm sure this is because of low sampling rate of HR tracking. I compare it over several days with Fitbit Surge. I'm a runner and take care about my calories intake an burning over day as well. That's why I buy the FR235. I understand the situation of some people which want to have a longer battery life instead of good 24/7 tracking of HR. For myself I would accept shorter battery life for accurate HR tracking over day. I think a good way would be to have several options in settings for higher sampling rate and lower battery life versus lower sapling rate for higher battery life instead of current options automatic and off. I think Garmin can be open minded to both sides of people an their needs.

I read through the thread because personal I'm sad about 24/7 HR tracking and from this calculated calories burned over the day. I'm sure this is because of low sampling rate of HR tracking. I compare it over several days with Fitbit Surge. I'm a runner and take care about my calories intake an burning over day as well. That's why I buy the FR235. I understand the situation of some people which want to have a longer battery life instead of good 24/7 tracking of HR. For myself I would accept shorter battery life for accurate HR tracking over day. I think a good way would be to have several options in settings for higher sampling rate and lower battery life versus lower sapling rate for higher battery life instead of current options automatic and off. I think Garmin can be open minded to both sides of people an their needs.

How are the calories burnt compared with the Surge?