How are burned calories calculated.

siberianex

Hi,

I have a Fitbit Blaze and it is connected to myfitnesspal.
I am 6 feet tall and 232 lbs and in my late 40's.

I went for a walk on the treadmill today at 3.5 MPH and walked for 45 min.

when I did a sync from fitbit to myfitnesspal, it showed that calories burned was 454.

I found a formula on the web which is:
Energy Expenditure(calories/minute) = .0175 X MET (from table) X Weight (in kilograms)
To get Weight into kilograms, you take your weight and divide by 2.2
MET from table for 3.5 MPH walk was 4.0 so:
.0175 X (4.0) X (104.45) = 7.3115 per minute X 45 Min = 329 Calories Burned.

Also using the myfitnesspal calculator here:
http://www.myfitnesspal.com/exercise/lookup shows me 300 Calories.

So I am wondering why I am getting roughly 100 - 150 more calories burned as per the sync that I actually burned as per the other 2 sources from above.

Dont get me wrong, I would love the extra calories burned in my favor, but I dont want to get false information.

Can someone help me figuring this out?

Thanks!

xsmilexforxmex

I think Blaze tracks HR, right? Might have to do with that. If it was higher during the walk the fitbit might account for more calories that a formula that doesn't assess fitness level/heart rate...

ETA: also, fitbit tracks your BMR and gives you calories based on that as well. For example, if your BMR was 1200 (for ease of math), 500 calories get added to your total over each hour. Not sure if it adds them into the workout counts but something to think about.

NorthCascades

I wouldn't trust any formula that uses METs as it's a very subjective way of describing effort or intensity. But I suspect the reasons your fitbit is giving such a high number are (1) it's fooled by your heart rate, and (2) it's including your BMR calories.

Tacklewasher

NorthCascades wrote: »

(2) it's including your BMR calories.

I'd vote for this.

You BMR is ~ 2400 per day (used to make the math easier) so every "normal" hour you burn ~ 100 cals just existing.

CyberTone

siberianex wrote: »

Hi,

I have a Fitbit Blaze and it is connected to myfitnesspal.
I am 6 feet tall and 232 lbs and in my late 40's.

I went for a walk on the treadmill today at 3.5 MPH and walked for 45 min.

when I did a sync from fitbit to myfitnesspal, it showed that calories burned was 454.

I found a formula on the web which is:
Energy Expenditure(calories/minute) = .0175 X MET (from table) X Weight (in kilograms)
To get Weight into kilograms, you take your weight and divide by 2.2
MET from table for 3.5 MPH walk was 4.0 so:
.0175 X (4.0) X (104.45) = 7.3115 per minute X 45 Min = 329 Calories Burned.

Also using the myfitnesspal calculator here:
http://www.myfitnesspal.com/exercise/lookup shows me 300 Calories.

So I am wondering why I am getting roughly 100 - 150 more calories burned as per the sync that I actually burned as per the other 2 sources from above.

Dont get me wrong, I would love the extra calories burned in my favor, but I dont want to get false information.

Can someone help me figuring this out?

Thanks!

MFP uses METs of 3.8 (not 4.0 as per your lookup table) for Walking 3.5 mph; so that would account for the slightly lower number, but not fully. MFP Calorie estimates from activities do include your BMR. That is why many users say that MFP overestimates and most users only log a percentage (50 to 75 percent) of the estimated Calories earned from logging them directly in MFP (i.e. when not using a synced fitness tracker).

The Fitbit algorithms use more than just body weight and pace to estimate Calories for step-based activities, such as incline change and variable speed from the GPS chip and your heart rate per 5 or 1 minute second intervals from the heart rate monitor.

All of these are just estimates, so they all will most likely provide different numbers. MFP and METs lookup tables estimate Calories burned based on statistical averages and will vary.

The Fitbit collects running averages of your data points for multiple variables over time and can fine tune the estimates the Fitbit algorithms provide. I have had good experience trusting the Calorie estimates provided by my Fitbit and synced with MFP for the past 1.5 years while staying in maintenance.

Edited to correct minute to seconds.

xsmilexforxmex

xsmilexforxmex wrote: »

For example, if your BMR was 1200 (for ease of math), 500 calories get added to your total over each hour.

I can't math!

Tacklewasher

xsmilexforxmex wrote: »

xsmilexforxmex wrote: »

For example, if your BMR was 1200 (for ease of math), 500 calories get added to your total over each hour.

I can't math!

Must admit, I had a post all written up about "blonds" and your "1200 (for ease of math)" etc, but I decided it was sounding mean when I didn't want to be mean, but I did laugh a little at it.