Where does Fitbit get its data for calories burned during various workouts?

[Ramond]

Hello everyone,,

Whenever I manually log an exercise, Fitbit seems to give me some unreasonably high number for calories burned and I always have to adjust it.

There are plenty of studies for how many calories are burned for typical exercises, but, for example, Fitibt will claim that 1 hour of weight training is 300 calories. However, Harvard Medical studies show that you burn on average 180 calories per hour in weight training.

I'm just wondering where does Fitbit source this information from and why does it seem so much higher than most published data out there???

[emili]

I lift weights and I have never seen 300 calories burned for that activity. In fact, in order for me to burn that many calories per my fitbit, I have to walk at least 50 minutes in a pretty fast pace or run for 25 at least 6 miles per hour. If you have the HR function your calories are calculated using your actual level of intensity derived from your weight, height, HR, etc. If you don't, then it is giving you an estimate based on the standard calculation of using the activity and your age, height and weight. If it isn't a step based activity, the calculation will more than likely be very estimated. 

[JohnnyRow]

First let's check your source.  Calories burned mean nothing without knowing weight.

I find a Harvard Medical saying a 125 pound person burning 90 calories in a half hour for weight lifting: general, and twice that for weight lifting: vigorous; and of course it goes up for heavier people.

https://www.health.harvard.edu/diet-and-weight-loss/calories-burned-in-30-minutes-of-leisure-and-rou...

[WavyDavey]

Just the term weightlifting is problematic. That can mean sitting on machines doing fairly light weights for 8-12 rep sets. Or it can mean grinding out heavy squats, deadlifts or olympic lifts. The difference in calories burned is enormous between the two types of exercise.

At 90kg, I could get 500 calories burned in an hour very consistently with heavy barbell training (I weigh much more than @emili). This is about in line with the MET calculations at around 5 MET or so. Fitbit does use the MET calculations when an activity type is specified.

https://www.hsph.harvard.edu/nutritionsource/mets-activity-table/