Can anyone speak to the algoritm

ITVGuy2000

Here's what I assume. MFP calculates total calories from the following:
Cardio Calories entered under exersize.
Cardio calories automatically entered by other applications (fitbit, other running logs).
Fitbit/MFP look at times to determine if there is an overlap between calories that are logged in MFP, and calories that are logged by Acitivity Trackers (fitbit). If there is an overlap, the redundancy is subtracted. Thus, this is how you get negative calories from fitbit.

Hey MFP/Fitbit, is this close to how it works?

NancyN795

Actually, you can get negative calories from FitBit without entering any Cardio Calories in MFP. I never enter any exercise in MFP any more. I always start the day with negative calories from FitBit. This goes away as the day progresses.

MFP evenly divides your expected calorie expenditure (based on the activity level you entered) throughout the day. This is reasonable because all MFP knows is what you (either directly or indirectly through FitBit) tell it about your activity and food consumption.

FitBit, properly, reports the calories burned so far that day. Early in the day, this generally is close to just your BMR because you've been asleep, so MFP will show negative calories until your activity level allows FitBit to "catch up" to what MFP expects.

ITVGuy2000

I still don't get how it comes up with some of the numbers I am seeing, and what you typed still doesn't sound complete.

Today for instance. Killed it at the gym. Two separate entries plus one from fitbit. All positive exercise calories. Now in the evening, over 10,000 steps, fitbit is subtracting calories. So at about 1pm my burn was like 750 calories. Now in the evening, my burn is 680ish. I don't know how I can end up un-burning calories.

Anyway, its all still useful. I know how about many calories I burned. And when I burned them. And what I was doing. I never put too much faith in the calories here anyway. I treat both burned and consumed calories as guideposts, not absolute values.

Anyone know any more on how fitbit offsets with MFP for burned calories?

NancyN795

You're not "un-burning" calories - obviously. However, you might be sedentary enough late in the day to start eating into the "bank" of exercise calories that you built up earlier in the day. That is, your rate of calorie burn - as calculated by FitBit - is less than the constant rate of calorie burn that MFP allots, so the FitBit exercise calories that MFP displays will go down. I'm sure this happens to me as well - I just pay less attention towards the end of the day. If you reduce the level of daily activity that MFP expects (mine is at "Lightly Active", so I could change it to "Sedentary"), then the effect will be less noticeable or might even go away.

heybales

You got it wrong when you included Fitbit in there.

Fitbit merely reports a daily burn to MFP, along with stat of steps taken.

MFP had an estimated daily burn based on BMR and your selection of activity level.
When you logged exercise it increased the daily burn.
When you took the deficit off, you ate more when you did more, you ate less when you did less. Same deficit.

MFP uses Fitbit's daily burn to correct it's estimate, that's all.
If that daily burn contains exercise, it doesn't know that, unless you happened to log it on MFP. And you should ONLY log non-step based exercise for the non-HR devices - swimming, rowing, biking, lifting, elliptical, ect.

So the calorie adjustment is NOT just exercise calories. It's merely the difference. You could have big adjustments on non-workout days, merely indicating you selected the wrong activity level on MFP.

Anything manually logged to MFP, or Fitbit for that matter, or synced in to MFP, or Fitbit for that matter (but don't sync to both sync MFP sends it over too), will replace the calorie burn estimate for the time indicated on Fitbit.

If you manually log or sync a workout in to MFP, it subtracts that along with estimate it thought you'd burn anyway, from Fitbit daily burn.

MFP estimated daily burn no exercise - 2500
Weight loss goal 1 lb weekly - 500 cal deficit
Eating goal non-exercise days - 2000

Exercise 700 calories and manually log it in MFP because it was lifting, and not seen correctly by Fitbit.

Fitbit reports to MFP you burned 3000 say prior to manual logging.

3000 - 2500 = 500 cal adjustment
Eating goal 2000 + 500 = 2500 eating goal. Still 500 cal deficit.

You manually log workout, which replaces Fitbit's calorie burn for that time.
Fitbit reports 3300 now.
3300 - 2500 - 700 = 100 adjustment
2000 + 700 + 100 = 2800 eating goal. Still 500 cal deficit.

And it shows you burned 100 more in the day beyond exercise that MFP wasn't aware of until that report.


Now you merely need to take that mid-day to do the math that you saw.

If Fitbit reports you burned 2000 by noon, because you had a big workout and synced at noon, MFP is going to do 2000 x 2 = 4000 daily burn - 2500 assumed - 700 logged workout = 800 adjustment to your eating level.

But after 100 cal increase in Fitbit daily burn, next sync go across to MFP, or if your device does sync again, it sends new data across. New math done.

So if by 6 pm Fitbit sends 2500, 2500/18x24=3333 - 2500 - 700 = 133 cal adjustment.

Now - what does effect the daily burn that Fitbit sends to MFP is a setting called calorie estimation.
If you sync device often doesn't matter, because fresh data is always correctly what is sent.
But if you don't sync often, it can inflate the assumed daily burn by Fitbit without a fresh sync.
Fitbit will assume daily burn is based on historical averages, and assume that much per hour, and send that over if no fresh stats from device.
MFP does the same math as above.
With calorie estimation disabled, without sync stats then Fitbit assumes daily burn will be barely above BMR level every hour, and send that smaller value over.

That setting is on website account at least, Log section, Food tab, Food plan - setting button for Personalize (calorie estimate enabled), or Sedentary (disabled).

Again, if big chunks of time between device syncs, but looking to MFP for what you can eat, the latter will cut down on big adjustments.