calories in/out, "starvation mode" question

Hi there folks. I hope I can phrase this question in an understandable way. Here is a bit of background.

I started logging my food and exercise here on July 1st. I was 275 and am 5'8". I started at the MFP recommended 1300 calories for a 2lb per week loss. I had selected sedentary as my normal activity level. I was also exercising. I did not eat back my exercise calories. After a couple of weeks I started Turbo Fire and about three weeks ago I did start eating back some of my exercise calories which put me up to 1550ish calories on most days. I almost always was making sure my exercise (based on HRM) was getting me an extra 500 cal a day burn. In the last three weeks I've only lost 1/2 pound. However I have lost 15 lbs overall so over I'm pretty close to averaging 2lb per week but just most of it happened in the first month. My diary is open if anyone wants to look. I have been absolutely anal about weighing and measuring my food with the exception of yesterday where I went out to lunch with a friend.

So a few days ago I got a Bodymedia Fit. It is showing that I burn 3500-3600 calories a day. These were typical days for me, not days of above average activity. At first I thought whoa! no way! But then I thought that if I had my MFP activity level set to "lightly active" rather than "sedentary" and ate back all of my exercise calories instead of some of them, it would not be the huge difference that it at first appeared. I thought myself sedentary since I just sit around a lot at the computer most days, but I guess I do get up like every 10 minutes and walk around, I just can't sit still very long without fidgeting. I've gotten up twice already just writing this lol.

Anyway, if this device is accurate, I have often been having almost double the calorie deficits on many days as compared to what I am supposed to be shooting for. However I have also read that if you have a lot to lose, as I do, it isn't that big a deal. Certainly my weight loss numbers though, have not reflected these large deficits, particularly in the last three weeks. I am not worried about it as I believe that three weeks is not really long enough to gauge anything by, with differences in hydration level, etc, I could get on the scale tomorrow morning and have a whoosh and be down 4 more lbs, however I have a question which is:

If one's body was perceiving too big a deficit in calories for it's liking and started trying to hang onto them (i.e. "starvation mode"),
would this not be reflected in a Body Media Fit type device as a lower calorie burn? In other words, there is no way that the body can "try to hang on to weight" other than my lowering my bodies calorie expenditure, which would be reflected by lower burn on the BMF? If the BMF is accurate I should have lost much more weight based on simple cal in/cal out unless there is some other way that my body can "hang onto weight cause it thinks there's a famine" other than by reducing my calorie burns. Not that I'm complaining, I'm pretty happy with my loss so far, and don't want to lose faster than 2 per week, but by nature I'm a data freak and just want to understand.

I'm going to be upping my calories quite a bit and try to maintain a 1000 deficit per the BMF for a couple of months and see how the numbers add up. This is kind of scary as it will mean eating 2000 calories or more on days that I have longer workouts. But I am very curious to see what happens.

thanks for any input, sorry for the long post!

ssdivot