Can there be to much calorie defict?

Yes, but the amount can be quite different for everyone, and will depend on macros, type of exercise, BF%, etc. In general the larger your deficit is the more muscle you will lose as you lose weight as a % of the weight loss.

Things you can do to lose less muscle, is a smaller caloric deficit, heavy lifting strength training routine, and adequate protein intake.

So if your goal is fat loss, the smaller the deficit the better.

The way MFP is designed you are supposed to eat your calories back. Be warned, however, that MFP vastly overestimated calories burned, so you probably should assume you burn half of what it tells you.

MFP is also designed for you to eat back your calories - a deficit is already in the goal, adding exercise makes your deficit larger than necessary, so its important to eat them back.

And yes, there is a such thing as too large a deficit. Since you only want to lose 14 lbs, your deficit should be modest. A person who has a significant amount of weight to lose can do fine on deficits of 1000 calories or more - for a period of time.

Most people here are strict purists - you *must* eat back your calories.

I'm ornery and I prefer to listen to my body. If I'm not hungry, I don't eat them back. If I am, I do.

It is possible to have a deficit large enough that your aren't getting all of your nutrition...i.e. your vitamins and minerals, but also enough healthy fats and protein. The biggest issue here is malnutrition. There are plenty of threads if you search in RE to people losing their hair, losing their periods, etc with too big a weight loss deficit.

Also, MFP is a NEAT method calculator. You need to do a little research on the tool and that method of weight loss. A NEAT method calculator assumes no exercise in you activity level...so any exercise is extra and needs to be fueled. Not to be confused with the TDEE method which does include exercise in your activity level and thus you would not eat back those calories. You need to understand the method you're using...if you're using MFP as intended, you're using the NEAT method...eat back most of those calories....also, I guarantee you that you got fat eating way more than 1900 calories.

It all really comes out 6 of 1. When I did MFP my weight loss goal was 1,850 net calories (to lose 1 Lb per week)...with my exercise, that usually came out to around 2100-2200 calories. When I switched to the TDEE method which included my estimated exercise activity, my TDEE - 20% (to lose 1 Lb per week) was 2,150...so pretty much the same.

One thing you definitely have to be careful of is overestimation of burn. Most data bases are pretty off...machines are a little better...HRMs are a little better than that...still, it's all estimation. When I did MFP, I shot for at least 50% of my exercise calories back and as much as 70% to account for estimation error. I always ate back something though unless it was a nominal exercise session or just walking less than a couple miles or whatever...but if I was doing anything intense, I ate back those calories. Don't get sucked into logging vacuuming the house and what not...that's just stupid, but people do it.

I know there's an impulse to try and drop weight quickly, but all you're going to do is lose a lot of muscle along with your fat and then look like **** when you're done.

Here is another math problem that is part of the answer...

Each pound of body fat can only release 31.4 calories per day. So you take your BF% against your total weight and come up with how much fat you have then multiply that by 31.4. If you have a deficit greater than that number, it cannot come just from fat and you are guaranteed to lose some lean body mass. You will actually lose some LBM even below that number; it just can't be helped. But above that number there is no way to make the math work.

ETA - getting proper nutrients was covered in other posts. This is a different component of the answer, not a different answer.

I told to eat back some of the exercise calories.