Using Fitbit to determine TDEE

Fitbit helped me get my TDEE baseline. I wear it 24/7 and just go about my normal days. I'd say get an average after wearing it for a week. I found out I fall between activity levels for most calculators and on MFP, I'm set to moderately active and going with TDEE - 20%. That's -500 calories per day to get a 1 pound/week weight loss.

Bit of a cut and paste iPhone job. . .


Thu 12/20/12 07:15 PM
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This is a topic that I'm really interested in because I bought my Fitbit just for this purpose. According to Scooby's workshop my BMR is 1490, my TDEE is 2310 and to lose weight at the rate I want to I should eat 1848 (I round up to 1850.) NOW. How does the fitbit help me figure this out? Do I look at the number of calories burned at the end of the day and see if it REALLY matches my TDEE? Is that what I'm supposed to do? I just got my fitbit yesterday and havebn't used it a full day yet. I have a ton of questions.

The same applies to all the levels. I guess I kind of think of the fitbit as making my own custom activity level. So in your case, I think I would probably compare the ending calorie burn to your Scooby TDEE to see how close you are to the level you chose.


I've looked up the past months data on Fitbit Dashboard. It tells me I've burned 68444 calories in the past 30 days.

68444/30=2281, so my average daily burn is 2281 calories.

Using a 20% cut I could set MFP to 1825 and ignore any Fitbit adjustments. I was doing this for a while, but I found the end of day adjustments really annoying, it's a personal preference.

Most of the BMR calculator sites put a daily burn of 2281 as moderately/very active. So I have MFP set to moderately active and to lose 1lb a week. MFP gives me 1500 calories. I've set Fitbit to also lose 1lb a week, so that both sites are the same and are talking sensibly to each other, I don't want them to argue about how much weight I want to lose. Both sites have given me a 500 calories deficit. I also have Fitbit set on personalised, it learns how active you are and gives you a daily calorie estimation based on that. In the activity section on the dashboard I have also set that to 2200 calories burned as my target, since that's my average, I don't think that makes any difference to numbers, it's just a target. So based on my average burn and my daily allowance I should 'earn' at least 200 through a Fitbit adjustment, which would take my intake to 1700, still leaving a deficit of 500.

Here's how this week has played out so far.

Day MFP Allowance Eaten Burnt Remaining
Monday 1500 1580 489 409
(No extra because I reset every Monday)
Tuesday 1909 1703 477 683
(MFP allowance 1500 + 409 from Yesterday)
Wednesday 2183 2513 308 -22
(MFP allowance 1500 + 683 from Yesterday)
This is what I have done. I'm using the iPhone app so each Morning I check my previous adjustment and add it on to today, so this morning I started off with 1478 (MFP allowance 1500 + -22 from Yesterday).

I know it's a lot to take in all at once, but I would give it a month to get some accurate numbers then try a system which works for you, either a 20% cut of your average burn, or a similar method to mine. As I said previously, I'm giving it 8 weeks on this system, to see how it plays out, then I'll have a better idea of what works for me.
Edited by evanesco on Thu 12/20/12 07:23 PM
 

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