How Accurate Or How Is the calories Burned Calculated? 10k steps - 15k steps

[Bruceleean]

Hey everyone! this is my very first post. However, not my very first time using my fit bit.

As mentioned on topic title... I've always used MyFitnessPal as the app where I log in my calories. However, I do have my Fitbit integrated. To avoid having to guess and manually input how many calories i've burned on the app I'm hope and have been hoping that the my Fitbit sync in " calories burned" for the day is correct. Cause I am trying to make sure I stick my deficit.... or my maintenance or whatever period in time I'm in for my fitness goal. I generally average between 10k steps - 15k steps... some days i walk slow, some days I jog the steps, which equals an increase in heart rate which means i'd burn more calories than walking the 10k steps. Then in addition i walk around the house, i weight train, cook, and stand. Anyways i just want to know how its actually calculated in the most simplest terms.... i'm 5'5 1/2 + 150lbs .. hitting my steps nearly everyday... I know this may have been asked before.. just was wondering if there was an alternative or a percentage i should go by to stay conservative on my calories burned numbers to ensure I'm not eating too much. THANKS!

[emili]

Hey there @Bruceleean I am not sure I follow your question. Are you asking if your fitbit is calculating your calories burned per the activity you are doing accurately? The calculation takes your BMR which it gets from a standard formula using your age, weight and height, plus your heartrate through whatever activity you are doing. The accuracy is probably almost accurate, but what you want to focus on is consistency not the actual accuracy of the number. If you get the same calorie burn for the same activity over and over, it may not be "accurate" but it is consistent enough for you to make informed decisions about your calories in. Hope this helps... 

[Bruceleean]

Got it... I just hope that it’s not over calculating calories that’s all. That way the earned calories I get for burning through myfitnesspal I can still hit my calorie goals

[Heybales]

I want to start with it sounds like confirming what you understand happens on MFP with linked accounts.

Fitbit sends daily calorie burn, MFP subtracts what it thinks you were going to burn with no exercise and your selected activity level (Sedentary recommended), the difference is in your Exercise Diary on a line about Fitbit Calorie Adjustment.

Positive if your day burned more, negative if you burned less and have option enabled for Negative adjustments (and aren't bumping against minimum 1200/1500 female/male limits).

It has nothing to do with exercise specifically, merely the difference.

For lifting manually log as Weights to replace the inflated calorie burn Fitbit got using HR. It's not a big calorie burn in comparison - and that is absolutely true, it's not.

So indeed the Fitbit side is how you confirm that MFP keeps the desired deficit no matter your level of activity.

Fitbit calorie burn estimates:

Base burn (all non-moving) is BMR calculated. Which for the vast majority of average will be within 5% of reality (even with thyroid gone), huge differences in BF% or muscle mass will throw that off outside 5%.

Daily activity is by distance your steps takes you.

Distance-based calculations are very accurate, better than 5% if no steep or constant incline. (because walking/running has been used in research studies on treadmills for many decades with measured indirect & direct calorimetry calorie burn).

Fitbit can dynamically adjust your per step distance based on stride-length setting and your weight, calculating between expected and actual impact to distance. But it's best if it's adjusting up and down equally for distance from a midpoint, and pace determines that.

So to tweak that accuracy, walk a known 1/2 to 1 mile distance at 1.8 mph (between grocery store shuffle and exercise pace) and confirm it got the distance right. GPS not accurate enough, track or calibrated treadmill.

Sitting awake is given BMR level burn, though burn more since awake.

Standing time is given BMR level burn, though you burn more standing.

No calorie burn given for the roughly 10% of calories burned from processing food eaten.

So good chance of being underestimated depending.

Exercise is by HR-calculation.

That is only a valid decent estimate (and even this can be thrown off) for steady-state aerobic - so same HR, not intervals up and down, and not anaerobic like strength training.

Anything else is inflated calorie burn.

Dehydrated or hot elevates HR for cooling, not because of doing more work and burning more calories - so inflated calorie burn. Stress will do that too, or very long workouts.

HR-based has limits.

But how much of your daily time or daily calorie burn is that workout anyway, even if inflated. If 15 min and very active otherwise - no big whup. If an hour and otherwise sedentary - big deal.

Running would still be best by distance-calc not HR. You can manually log a workout by distance and time and get better estimate if going for long periods of time for a run. The last workout entered (manually or synced in) replaces whatever is there, like Fitbit estimated calorie burn.

The low end of the aerobic range is also not a good fit for HR formula, most inflated there, and at the top before going anaerobic.

So your walking with a few jogging moments is inflated for sure.

Unless again, it's like 15 a few days a week, in which case don't worry.

Oh - ignore the generally thrown out MFP advice to cut your exercise calories by 50%.

As stated - the adjustment may show up in the Exercise diary and as exercise in the math - but it's not exercise, and most important it's not calculated from a database.

That advice came about because unlike Fitbit being a replace-only system, MFP adds workout calories to an already daily burn that includes activity during all minutes.

So slow long calorie burns like walking may burn say 150 calories per hr and that database entry is correct, but MFP already expected you to burn 85 anyway by being Sedentary, and it just added the 150 to the 85. So talk about slowing down and ruining the deficit.

But with a linked account, the deficit comes off what Fitbit says was daily burn. So their advice is wrong, especially since its spouted without asking, even sometimes with knowledge of syncing.

Dittos to no matter what system - adjustment will be required based on actual results.

As long as you don't make the deficit unreasonable and cause stress to body and increase water weight which has no calories - your results dictate the real deficit.

Errors can come from food or exercise side of the equation.

So then you adjust.

[JuanJoFitbit]

@emili @Heybales, thank you so much guys for your great input and valuable information.

I would like to know if you have additional questions in regards the calories burned calculation. I'd just like to add this help article, which explains basically how your Fitbit device calculates your daily activity, including calories burned.

See you all around and please stay safe.