Why do probably the majority of women get 1200 cal daily NET goal?
You enter age/weight/height, MFP calculates BMR but doesn't show you what it is (unless manually done - Tools - BMR calc).
You enter activity level, which may have little to no bearing on reality, which takes BMR times some multiplier (1.25 for sedentary), for a daily maintenance NOT including exercise.
You enter a weight loss goal (women of course select 2lbs wkly usually) that may or may not be wise, MFP says recommended 1lb (which will see may still not be wise at some point).
MFP takes daily maintenance minus weekly goal lbs * 3500 / 7 (daily deficit) = daily goal. Unless it falls under 1200, in which case you get 1200.
You are shown your Goals page where those facts are spelled out with confusing inclusion of your goal exercise amounts and calories - which have NO bearing on the math.
But several places on this page use a phrase not used everywhere - "Net Calories Consumed* / Day" and "Net Calories Consumed*" and footnote "* Net Calories Consumed = Total Calories Consumed - Exercise Calories Burned".
But it also says "Your Daily Goal".
And of course your Food Diary page says after logging exercise - "*You've earned XXX extra calories from exercise today" and changes Your Daily Goal automatically.
How can that be that eating more can lose weight?
BMR is basic metabolism for functions of life if in a coma 24 hrs, it needs so many calories to do all those functions. If it doesn't get them, the body has great survival mechanism, by just not doing some of them, in essence slowing down. (staying warm is easiest thing to stop, unless just really required for core temp. Muscle repair, muscle growth impossible, growing hair/skin well, fluid levels in every cell dealt with most required function still done as best as possible). Since this is energy supplied to all the cells, it must be taken in. Otherwise we'd all have little perpetual motion machines in our cells, and could just stop eating and lose just fat because there is plenty of it. That of course doesn't happen.
So what the body was willing to spend 1500 calories burning to accomplish, it now only has 1200 to do so, and it does so.
With a slower metabolism though, all your other activities in addition to sleep now burn less too.
What daily activity used to burn 800 calories on top of the 1500, now becomes 500 for instance, on top of the 1200. So lost 600 total calorie burn because of eating 300 less calories.
There is a lag time for that - based on how much yo-yo dieting you've done and how fast your metabolism has seen this before, how big of a total deficit compared to previous eating level, how big a deficit under BMR now, genetics, food eaten, ect. 3 days in some studies, some on here find 3 weeks possible if the stars align well, because of those factors.
That's if you net at 1200 because of eating back exercise.
Stop doing that because what used to be an 1100 calorie deficit (2300-1200) to previous eating level has slowly dropped to 500 cal deficit (1700-1200). So what started as 2lbs week at some point has reached 1lb.
So you either start exercising more or drop cal's or stop eating back exercise lets say.
So now eating at 1200, exercise takes 400 of that daily on avg. And that 400 is already less than it could be because of slower metabolism.
So now your body has 800 to work with, what used to take 1500 to do. Every thing slows down more.
Eventually, you have reached the wonderful level of:
800 NET for BMR, so that is BMR, * 1.5 for moderate level of exercise 5 times a week = 1200.
Congrats - now eating at maintenance level!
Now, literally, what studies have shown happens is not that the actual BMR lowers that much, because there are functions the body just must do to keep you alive, so it will get the calories it needs for bare basic functions, and other functions that your Resting Metabolic Rate would be performing are lessened, or other movements normally done during the day are lessened. The effect ends up being the same. You reach equalibrium, and eating at maintenance.
2 directions, eat even less or exercise even more - I hope obvious what will shortly spiral out of control in that direction.
Or eat enough to feed BMR and exercise, and let your daily activities that use mainly fat for energy create your deficit and burn it off.