Fat Burning Question + Plateau

I sent this to a friend by PM the other day who asked me about my program. It may not be entirely accurate as I'm not as knowledgable as some of these other folks, but this is how I understand it.

TDEE is your total daily energy expenditure. That is BMR+NEAT+ exercise.

Let me explain it like this. Your BMR is your basal metabolic rate which is fairly accurately predicted by MFP. This is the calories your body needs to perform all those involuntary tasks like breathing, digesting, etc. Everything else is activity. It's the everything else that MFP fails to predict. Exercise calories are a given. But then you have calories for getting out of bed, typing on your computer, brushing your teeth. All of those activities are your NEAT calories or non-exercise activity thermogenesis. BMR+NEAT+exercise = TDEE. If you do not eat enough calories to supply the body with this required amount of energy, then it will draw upon itself to make up the difference. Any and all tissues are available as an energy source, but it also has the ability to prioritize to preserve necessary functioning. The more grossly obese you are, the more your body will be dependent upon fat storage. However, the body will not deplete fat stores all at once if the difference between your caloric intake and your TDEE is greater than 20%. At that level, your body will draw upon both fat and muscle. If you have large storage of fat, then it will be more dependent on the fat than muscle but it still uses both. Now remember, fat is necessary for the body to function. So, if you use your large stores of fat rapidly, then the body will switch gears and use more muscle than fat. If you have reached this point, and you are strength training, then you are really only creating muscle to be used for energy. Basically, you are negating any benefit that might come from strength training and, theoretically, you would be on a plateau with your weight loss.

The tricky part is how to evaluate your TDEE. As I said, MFP really cannot accurately predict TDEE so they create their deficit based on BMR. However, your NEAT will vary from day to day so using this method will likely keep you well below the 20%. Devices like the BodyMediaFit and the BodyBugg accurately track your activity but they can be costly.

What I do is I have a FitBit. It was a one time cost of $99. It is a pedometer that monitors all of my steps and even some other movements. It records my calories burned and automatically updates MFP. I changed my calorie goal to maintenance and presumed that figure to be my BMR+NEAT. Then I allow MFP to add in the calories recorded by the FitBit. I presume the new calorie goal to be my TDEE. I multiply that number by 0.8 and whatever remaining is my daily calorie goal. I eat no less than that amount. So far, it has worked well for me. I'm losing inches dramatically. I haven't seen a significant difference in the scale but I have stopped using it as the indicator for my progress. If I stop seeing progress in inches, I will probably go back and change my MFP goals back to my BMR and go from there. But for now, I'm happy with my method. I hope this helped.

What are your stats and how much are you currently eating per day?

I'm 12 years older than you and pretty small and I definitely don't eat the usual 1200 per day.