Margin of error between calories and real weight loss

BlackJack96

I've been doing MFP since the start of the year and as you can see from my signature it's been working. One thing I've noticed is that I have not been eating back my exercise calories (but still netting at 1200+ so I don't go below by BMR) and yet I am still losing about 1 pound a week. (I am set to lose a pound a week on my basic plan so I figured I would lose more by not eating back the exercise calories).

Anyways I did some math assuming a pound is 3500 cals and compared my actual weight loss based on the scale with my caloric weight loss based on the Fitbit data (which is fed from MFP).

So In the same time zone (74 days since I got a fitbit) that I lost 9.8 pounds I supposedly burned 55479 more calories. If you do the math 55479=15.9 pounds. I extrapolated this out and Found that by my real weight I was losing 464 calories per day but by calories I was eating a deficit 750. Overall this accounts for an error of 10-15% per day in either my caloric intake calculations or caloric output. (Assuming 2020 calories in and 2510 calories out at baseline). However, this small error results in a major difference in the calorie differential and eventual weight loss (about 50% difference).

I guess my point in all this is to see if this is something that others are experiencing as well (i.e. their expected weight loss is mathematically different than their actual weight loss)?