Help me!!! I bought a Fitbit

KwaziiNeko

I bought a Fitbit flex today and I still don't understand how it'll tell me how many calories I burn.

shadow2soul

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KwaziiNeko

So whatever calories I burned would it automatically sync to Mfp?

shadow2soul

Now, what that doesn't say is that Fitbit divides your BMR into 15 min time segments and will only add the calories for time that has actually passed. So my BMR estimate ends up working out to 13 calories every 15 mins. So at 12:15 am, I will have 13 calorie burn. At 1 am, I will have 52 calories burned.

Calories from tracked "steps" will be added to your BMR. Speed/impact seems to determine the calories you get from your steps. They don't really elaborate on this anywhere. It does however seem to know the difference between difference speeds of walking/running and for me has been pretty decent at estimating the calories burned for such activities.

shadow2soul

KwaziiNeko wrote: »

So whatever calories I burned would it automatically sync to Mfp?

yes. It sends your calorie burn over at your last sync, MFP uses that plus your activity level setting to estimate what Fitbit is going to say your full day calorie burn was at TDEE. It then takes that number and subtracts it's original guess from it to come up with an adjustment.

Example:

MFP predicts at lightly active I will burn 1796 calories per day and bases my calorie goal off of this number.

That's equal to 74.83 cals per hour / 1.247 cals per minute (this comes into play later).

My last sync was at 7:01 pm. Fitbit had a calorie burn of 1740 at that point.
There is 4 hrs 59 mins left in my day after that sync.

So MFP does this:
74.83*4 = 299.32
1.247*59= 73.573

1740 (from fitbit)+ 372 (remaining time left in day estimate) = 2112

2112 - 1796 = 316 calorie adjustment to the calories I can eat for the day, because I burned more calories total than MFP's original estimate.

KwaziiNeko

Hmm interesting
I hope I didn't waste my money buying this product
I just need something that'll accurately tell me what calories I'm burning

shadow2soul

KwaziiNeko wrote: »

Hmm interesting
I hope I didn't waste my money buying this product
I just need something that'll accurately tell me what calories I'm burning

There is nothing on the current market that will be 100% accurate. The tech just isn't there yet outside of a lab setting (even then I can't say for sure that it's 100% accurate). I've used a Zip & Flex, found that with accurate logging the calorie burns from them were underestimated by about 200 calories per day on average. Using the Surge currently (one of the models that uses HR to an extent to help with calorie burn) and it is been pretty dead on with my calorie burn. Use the estimate and then adjust up or down based on what actually happens with your weight over a 4 week period. Actually Fitbit makes this part pretty easy. On your profile page it will have a 30 day average calorie burn and a 30 day average intake. Subtract the 2 and you get a 30 day average deficit. Multiply that # by 30 to get your total 30 day deficit. Divide that by 3500 to get your expected loss. If it matches what you lost, then your Fitbit is accurate enough to go by. If it's off, then it's either over/under estimating or your logging is a bit off or some combination of the 2.


(by accurate logging I mean: food scale for solid foods, measuring cups for liquids, double checking that the entries I pull from the database are correct, no entries that start with " Homemade ", avoiding any quick ad's)