Calculating TDEE averages, am I doing this right?

EpicMedic

Ok, so I have a 21 day spreadsheet in front of my I just exported from my Bodymedia. According to it, I should have lose 9.9 pounds in the 21 days I have used it:

Total Calories Burned: 82975
Total Calories Consumed: 48489
Total Deficit: 34486 / 3500 = 9.853 pounds

However, Since I started using the Bodymedia I have lost 7.7 pounds, with a lot of that shedding in the past few days when I was more observant of my sodium intake and late evening carbs. So, given that I have exact numbers on my intake for the last 21 days, is this math correct:

I have lost 7.7 pounds, which equals 26950 calories.
26950 divided by 21 days is 1283 calories per day
I have eaten 48489 calories over the last 21 days, which equals out to an average of 2309 calories consumed per day.
If I add the calories I have consumed to the deficit I would have had to have have had to lose 7.7 pounds, so 2309 + 1283, I get 3592.

Is my TDEE 3592 then? That adds up to 7.7 pounds worth of a deficit over the 21 days, plus my average consumption.

My Bodymedia is giving me an average caloric burn of 3951 per day. They are supposed to be "90% accurate". whcih 90% of that would be 3556 calories, which is VERY close to what I'm calculating. Is my Bodymedia just overestimating by 10%?

Any help with this would be appreciated, I just had my first EVER BF% measurement today, a DXA scan, and I read 27.5% body fat... It's higher than what I expected, and I'm looking to use that as some raw motivation to really get down to business. If I'm doing this calculation wrong, how would it be done right? Is 21 days a decent sample time, or do I need more time tracking before a good result can be had? Show me the love, MFP!

Todd

4legsRbetterthan2

Looks like your math is correct, kudos.

A few things to remember-

Weight loss is not always linear and direct due to several factors but the biggest is usually water retention/dehydration. I am not sure how often you weigh yourself? Make sure you take your weights using the same scale under the same conditions and take an average from a few days to get your numbers for comparison. I think having a longer time period would help you too, I usually don't see the loss I want over a week but over a month or 2 months I will be spot on.

Another frequent trip up is the food logging. Since you are getting really nitty gritty with the numbers you really need to weigh everything. The "measured" serving sized on the containers (I think) are size estimates based off the weights. For instance there can be a pretty big difference between a tbsp and 28g of peanut butter, both of wich are listed as the serving size, and with a calorie dense food like that it could mean a 50 cal difference. If you eat alot of peanut butter that could really add up!

I can't really say about the accuracy of you Bodymedia, sorry no help there.

I am loving the dedication and you have really given this whole thing alot of though, keep it up!