If you are really good about logging your calories you may want to check out "Digifit" it does sync with MFP and Bodymedia and has some trend charts that may help you see what you may want to tweek. If you are a numbers/tracker geek you would probably enjoy it. I like it because I use a HR chest strap to exercise and it is great for seeing detail.

Is this an app or a device?

Remember, even if you log every morsel that goes in your mouth it isn't possible to be 100% accurate on calories consumed. The FDA allows up to 20% (yes 20%) margin of error for noted calories. So if something says it's 500 calories, it could really be 600. Add that up over multiple foods for a given day and that could easily result in a 200+ calories that aren't accounted for in the log. And considering there will be some errors due to portion sizes being off, missed foods, etc. there could be hundreds more calories not accounted for.

I thought maybe my BMF was overestimating my burn, but I always worked on the premise that if I logged 1500 calories I actually at 1500 calories... I never really thought about those extra calories due to the margin of error, etc. I'm starting to think it's more an issue, for me, with calories consumed than my log.

I will say I'm very happy I have my BMF and have found the information it provides very helpful. Recently I started taking some Zumba classes and my BMF would often show my calorie burn around 450 for a 1-hour class and I was working my butt off. I was expecting more, especially since I've seen lots of people with much higher burns, some around 1000 cals, doing Zumba. If I had just assumed around 800-1000 calories burned, or used the ~700 cal burn in MFP I would have been wrong.

I haven't ever compared what I should be losing to what I am losing, but it seems pretty accurate. I think I'll start the spreadsheet, though, just out of curiosity, and because I'm a data nerd.

I have noticed that it is fairly accurate for some types of exercise and not with others....After using it for a couple of months I looked back over my data and noticed that the weeks that I maintained around a 500 to 800-- calorie deficit, I lost around a pound....when I maintained a 1000 - 1300 I lost about 2 lbs. ( I do not know if accurate or not...but I know it is consistent for my body....so I just try to end my day with a constant deficit for the weight loss I want)

Also a lot of the issue with planned activities...I am an elliptical nut and the body media does not get the elliptical right even with the adjustment down closet to the elbow. So for my planned workouts I always take off my Body Media and use my Heart Rate monitor instead...I then go in and manually enter that activity and calories burned...Using these two methods has been great for me and has made the weight loss more consistent.

I had the same issue on my recumbent bike. I ended up moving the BMF to my upper left calf and it seems to log more accurately.