Question about eating below your BMR

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BMR and TDEE are estimates/averages based on statistical analyses. If you want you can calculate your own estimate of TDEE, based on logging what you consume and how much weight you lose, but even then, like the previous poster said that personal estimate can vary a lot.

BMR is not a magic line or switch, below which the body shuts down. It just doesn't work like that. Excessive caloric restriction over a progressive amount of time will have some health consequences, but it has to be over quite a long time (months), and you'd have to be pretty lean to start with. If you have a lot to lose (I was classified as BMI "obese"), then it can be extremely motivational to see the pounds come off quite quickly to start with, as long as you realize it's probably not sustainable, and you'll have to increase that over time.

Honestly, what I found most effective was to go with a calorie target, eat like that for a few weeks (weeks not days) and then just see what happens and how you feel. MFP recommended 1200 calories for me to start with (I'm a shrimp compared to you!), and I did that for a couple of months, until I felt the weight was coming off too quickly, so I upped it a bit, waited for another 2 months and then adjusted again. Seems to work OK.

Pardon me, for hijacking your thread OP, I have a similar question to anyone. I am male, 6'0, 312, according to MFP, my BMR was 2800 (estimated obviously) when I started, I changed my goal to 1800 calories but unless I go out to a restaurant and eat a 1000 calorie meal, I have a hard time eating up to my goal. More often I eat around 1250 average. I've been able to lose weight but hoping the progress doesn't slow down because I eat too little. Do you think that's too little or should I stay on this track?

I have a BMR of 2,084 and a TDEE of 2,801. I have read on here in multiple threads that you should not eat fewer calories than your BMR because of the health concerns. However, MFP recommends that I eat ~1650 calories a day to lose 2 lbs/week. This is confusing to me and not sure what the best route to go here.

Any help is appreciated.

Hi there... Your numbers are about in the ball park, looking at various calculators that I've been using off and on.... Remember, you will have to recalculate and adjust your nutrition as you are losing weight. MPF only stops at 1200 calories per day.....sort of an emergency break, I guess...but they have no shame 'underfeeding' someone with a reasonable number like yours.
My personal experience is, that I have to have 1500 calories (female 5'5", 50 yr, 135 lbs, that's why I can go lower...), or my body will run out of energy real fast. I can still workout all day, but this is the minimum food that I require before I tear up the fridge door.
My suggestion would be, eat anywhere between your 2 numbers for a few weeks, and see how it effects your overall wellbeing, If you feel like you can stay within your limits, exercise included, only then worry about your actual weight loss. And you will be losing, if you stay active, anyway, as long as you don't overeat. Everything you do has to fit into your lifestyle. If you can't manage, your fitness goals will eventually fail.
Also, you are tall. As your body composition changes, you might end up being much happier with only a few pounds lost on the scale after all, but might enjoy a leaner look with lot of lean muscle mass gained.
Good luck!

Regardless of the very good points about the accuracy of your calculated BMR...

There's nothing magic about your BMR number. Your body will draw calories from fat stores to burn to fuel "BMR" functions, same as activity functions. Nothing bad is going to happen to you specifically because you eat below your BMR.

That said...things can go south for you if you're not eating enough, that's a certainty. At your stage of the game, these things would primarily relate to energy levels as well as adherence (as in, if you don't eat enough then you're far more likely to binge than if you eat at a more moderate deficit). Further down the road, there are additional issues, but right now, that's what you're looking at.

The reason BMR gets thrown around is that it's a very, very good ballpark number of what the bare minimum of "enough" for most people. However, the bigger you are, the larger deficit you can sustain. Eat at the deficit that works for you, both in terms of being large enough that you're losing at the rate you want, while being low enough that you're appropriately fueling your body and activity levels and meeting your nutritional needs. More likely than not, that number will put your calorie goal above your BMR. But don't stress if it isn't, there's nothing special about that number.

Also, if your TDEE is ~2,800, then 1,800 calories/day would be the right number for 2lbs/week.