I don't think my fitbit is counting my calories burned correctly

[albeetie]

Okay, I'm frustrated because it seems like whenever I work out with a friend or do a group class, everyone burns way more calories than me! Why is that? I am fairly small and in shape (120 lbs. 5'7). I will do HIGH FIT (high intensity cardio class for an hour) and everyone will burn 500-700 calories but I will only barely burn 400! And I swear to you I am working out hard and not "modifying". Same thing with other exercises... other ladies will always burn way more than me. 

Why is that?! Am I not using the right exercise mode? I always just use the "workout" mode on my charge 2. 

Someone please give me some insight!

TIA

[jordan.van.dyk]

Hello

Calories with a fitbit( or any fitness tracker for that matter) is an estimate.
Your daily estimated calories ( assuming you plug in everything correct) should be fairly accurate as this will be a TDEE (Total Daily Energy Expenditure) calculation which will be based on a formula for determining BMR(Basal Metabolic Rate) or RMR(Resting Metabolic Rate) multiplied by a constant that corresponds with your activity level. You can see the standard formulas and how much they differ here https://www.sailrabbit.com/bmr/ . Anyone I know that has gone in to a lab to get their BMR /RMR measured has seen at most only a couple of percent difference than what the formulas produce for them.

Exercise is a completely different beast entirely, the only way to currently accurately measure this is to hook yourself up to a machine that monitors how much oxygen and carbon dioxide you are breathing in and out. Otherwise for fitness trackers it will use HR and a few other metrics to attempt to estimate it, for something  that is consistent  such as a long bike ride, or a long run the calculations will only be off 5-10% as mostly cardiovascular workouts are much easier to estimate. However even then a Stanford study from last year found that fitness trackers can be 20-93% off on their calculations (fitbit was one of the more accurate ones) http://med.stanford.edu/news/all-news/2017/05/fitness-trackers-accurately-measure-heart-rate-but-not... you can find the link to the study in that link as well. I did notice that fitbit has adjusted the calories for runs after the fact to be more in line with the study so at least for running (I don't bike or swim so I'm unsure there) it's more accurate lately.

Another thing to consider is 2 people doing the same exercise will not burn the same calories an example is earlier this year I was burning close to 450 calories for a 5k if I run the same pace for one now it's much lower close to 320ish. A lot of that is due to weight and overall fitness level, since I am down 35 lbs and my cardiovascular fitness is much higher running the same distance at the same pace no longer burns the same amount of calories.

I am unsure how everyone else tracked their calories but while it is possible that they burned 1.5-2x your calories it's also unlikely. Unfortunately for weight workouts, or high intensity fitness classes there is no way to accurately measure this except for wearing a mask like I mentioned above and even then it's hard simply because there is an affect called Excessive Post Oxygen Consumption. In general EPOC is much higher for certain high intensity or anaerobic exercise with effects still happening up to 38 hours after the exercise. I'm unsure if Fitbit attempts to quantify what you will burn in the future from EPOC as part of the calories of the workout itself.

The take away is there is no way to make it the correct amount and the estimate for calories burned during a workout should be taken very much with a grain of salt. If you are trying to determine how much you can eat while still losing weight. That does make it a bit more difficult overtime the TDEE should be accurate and ideally you want to just eat less then that. 1lb of fat is approximately 3500 calories, so if you average 500 calories under your TDEE per day you should lose approximately 1 lb a week. In the long run this tends to work out. As an anecdote  I ran a 1000 calorie deficit for 5 days a week and allowed myself to eat up to my TDEE on the weekend which left me at a 5000 calorie total deficit for the week. Over a 6 month period I averaged losing 1.4 lbs a week which is nearly exactly what a 5000 calorie deficit would be. Everyone is different of course so your mileage may vary.

I know I didn't answer very directly, as it's not a simple problem hopefully though some of what i said you can find useful and use the data your fitbit gives you in an effective manner.

[Yoly1977]

I have exactly the same question, I couldn’t have written it better!