I am so confused?!?!

I just mainly use what MFP have set out for me and adapt to it. I haven't bothered too much with other sites and everything with TDEE, but this does work.

The MFP method is set up to allow for you to lose 2lbs/week.

Any exercise you do, they encourage you to eat back the calories for it during the day, though I don't always do this , mainly depends on how I feel on that day really.

And after a week or so of counting calories, update your weight, if its changed , update your weight on the site, and it'll change your daily calorie limits accordingly.

It would be simple if everything was the same answer but TDEE and BMR are different (and I don't even know what IBM is).

It is simple actually.

BMR = Basal Metabolic Rate. When you hear "basal" think "base"...this is your base rate of calories that your body burns just being alive. You would burn roughly this many calories doing absolutely nothing except being.

TDEE = Total Daily Energy Expenditure. This is the total of all of the calorie you burn in a day...this includes your BMR calories, your NEAT calories (those calories your body burns doing day to day stuff like working, cleaning, doing dishes, etc...you day to day hum drum) and your exercise calories or EAT (Exercise Activity Thermogenesis).

BMR + NEAT + EAT = TDEE

The vast majority of your bodies calorie requirements are just BMR...for most people, this represents about 70% of daily calorie requirements. Then you have your NEAT and your EAT...for the vast majority, your NEAT is going to make up the second largest chunk of your calorie requirements...roughly 20% (more for a sedentary individual and/or someone who does little exercise)...and on average, exercise represents roughly 10% of an individuals calorie needs (obvious exceptions would be athletes and individuals who exercise excessively or individuals who do little to no exercise). I'll use my numbers to illustrate further...

BMR (1,850) + NEAT (510) + EAT (300 averaged out over a week) = 2,660 calories. This is roughly the number of calories my body needs to maintain weight. Through trial and error and working at this for over a year I know those numbers to be fairly accurate.

So to lose weight, I merely take a cut from the 2,660 calories my body needs to maintain weight...if I take a 500 calorie cut to lose roughly 1 Lb per week, I would need to consume 2,160 calories. Exercise is already included in the formula above, so I don't eat those calories back. With MFP, exercise estimates are not accounted for in your activity level...they are accounted for after the fact...this is why you have a NET goal with MFP and are given add'l calories to "eat back" when you exercise.

There are pitfalls to either method. With TDEE it is easy to overestimate your activity level as the descriptors are rather general; with MFP it is easy to overestimate burn given that data bases are notoriously off and even HRMs and such are not 100% accurate and become less accurate the further you get from an aerobic event. With TDEE you also have to be pretty consistent in your exercise regimen...if you get off course and miss exercises or start exercising beyond your original inputs, your formula becomes invalid. That's actually one of the benefits of MFP...if you fail to exercise, you don't get punished...you just eat to your goal and still lose because exercise is just extra activity...with TDEE, if you fail to exercise, you formula for weight loss is completely jacked. With either method and calorie counting in general, underestimation of intake is common as people generally fail to weigh and measure portions...eyeballing portions and ingredients has been known to result in as much as 20 - 30% error in estimating intake....that's enough to wipe out any deficit someone may think they have.

Keep in mind that this is all estimation. The numbers you get from these calculators are based on statistical averages...you may or may not fall into those statistical averages...and even if you do, nobody has a TDEE of exactly XXXX calories.