I ignore the burning too much message because it seems to happen to everyone who is active and wears a fitbit. I have used my weekly calorie burn from previous weeks to set my "weekly exercise calorie goal". It is that weekly exercise calorie goal that influences your Spark allowance and when it posts the "burning too many calories" message.
Here is what I do, to get my Spark allowance to accommodate my activity but not inflate it too much. I haven't really figured out how Spark calculates our exercise calories, but the minutes are from our Fairly active and very active minutes on fitbit, and the calories seem to include our BMR (which Spark already credits us for).
Spark uses Harris-Bennedict to estimate our BMR, fitbit's estimate for my BMR seems very similar to Mifflin. I already know that H-B gives me 120 more calories than Miffling for BMR. So I subtract 120 + 1 calorie per fitness minute from my weekly total and set that as my weekly exercise calorie goal. I also round up to make it an even 100 type number for my own convenience. (My sedentary/bmr calorie burn on fitbit is about 1 calorie per minute--I think a little less but I don't want to mess with fractions). I don't do this every week though, I just want to get in the right ballpark so the lower end of my Spark range is what my fitbit allowance would be on a sedentary day (though you may not have sedentary days).
I know it is confusing so I will give last week as an example. My exercise calories were 4113 and my minutes were 1051. If I subtract the 120 and 1051 minutes from 2113 I get 2942 calories. To round down to 100 I would enter 2900 as my weekly calorie burn goal.
The other thing is on the fitbit food plan I enter my goal weight and choose how quickly I want to lose weight. Then I look at the date fitbit predicts I would reach this goal. In Spark, I enter the same goal weight and for the "deadline" I want to reach goal I enter the same number that fitbit predicts. This is what effects your rate of loss on Spark and it directly effects the allowance--sometimes more obviously than the exercise calorie burn goal. Setting your deadline for a closer date results in a smaller allowance than a more distant date (but it will warn you if you pick a date that would result in more than 2 pounds a week lost or if it would put your allowance too low).
| December Minutes: 511