Fitbit Calorie burn & eating correct amount of calories

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Hi,

I hope someone can help me here. I managed to put 5 pounds last year and keep struggling to get rid of them. Few weeks ago i bought myself FitBit One as i was doing everything i should with no results . I was exercising 5 times a week ( running 3 times x 6 miles per run or more and weight 2 times a week. I use Heart rate monitor and i burn around 2500 - 3000 per week). On top of this i also walked a lot each day . I was eating around 1300-1400, and 1700 or little bit more on my running days.

I think the reason i am not loosing any weigh could be that i am no eating enough.

Now with FitBit i get a report and i burn around 2200 - 2600 calories a day. I think this is correct as one day i wore Heart Rate monitor for 24 hours and it gave me similar totals

My TDEE using fitnessfrog.com is 2048 and BMR is 1321.

My question would be how much do i eat? Does anyone using FitBit information and adjust calorific intake?

Thank you