MFP and Fitbit exercise calories WAY different

silkchicken

Hi! My Fitbit (Charge 3) is connected to MFP. Fitbit shows that I burned 637 calories on a walk today (avg bpm 121, 96% fat burn; not including the steps I've walked casually around the house). On MFP it shows I've burned 146 calories (it showed 326 a few hours ago though??) throughout the whole day, which is nowhere near the 637 my Fitbit has logged just from the walk. The step amount is the same, only the burned calories from exercising are different.
It happens every day. Why is the difference so big?

Maxematics

Because of the activity level you set yourself to on MFP. For example, if you chose that you are "Active" on MFP but the amount of activity on your Fitbit is less than what MFP sees as Active it will adjust your calories by subtracting some to make sure you don't overeat. Similarly, it will add extra calories if you exceed the activity level you set for yourself.

As a sidenote, the 637 calories you burned during your walk includes your Basic Metabolic Rate which is what you would have burned if you weren't walking. For example, if your BMR for the duration of that walk was 100 calories, you'd technically only have 537 exercise calories, not 637.

In any case, it seems like you only slightly exceed the activity level you chose for yourself. Most people, including myself, set themselves as sedentary and let Fitbit make all the necessary adjustments from there.

heybales

That Calorie Adjustment is merely the difference between Fitbit Total Calories Burned and what MFP estimated you'd burn with no exercise and your selected Activity Level.

If you were to exactly match that activity level except for the workout - then the adjustment would match what Fitbit says the workout is.

But you'll never exactly match - which means perhaps the walk got you tired and you sat longer later than you would.

Be prepared for another gotcha if you hit the couch early and then bed, and look at your eating goal and try to meet it then.
MFP was estimating the remaining hours of the day at your selected Activity rate.
Fitbit the next morning will inform MFP your burn rate was only BMR level.
So less calories.
If you hit your goal, the next morning on review will show you went over.

That amount is about the same if your evening routine is about the same - so prepare for it by leaving that much in the green uneaten.
The higher your activity level, the worse the effect.
Hence the advice to set to Sedentary.