Why add exercise calories to my base calorie while losing?

Have look at the "newbies read this" topic at the top of this section and you'll see that there is a lot of discussion around this.
I think it is important to remember that MFP has calculated a calorie deficit for you when you it calculates your calories for the day, so when you eat your exercise cals you still have enough of a deficit to lose weight.
Your body needs good fuel to function well, specially when you are exercising.

This is just my opinon on the matter, however I am trying to build muscle.

When your food intake is low, your body starts to use fat as energy, which is good but the aftermath isn't. Your body then stores more fat then usual next time you eat, in order for the fuel to be there next time you do any type of excercise. Regardless of gaining or losing weight, you should be eating a certain amount of carlories daily, and then comphensating for any excercise.

Basically, your 1200 calorie diet becomes a 1100 calorie diet, forced your body to store more fats to use as fuel during the next meal. You may not feel hungry, or you may not record it, but maintain a balance of positive calories in the log ( food ) and negative calories ( execercise)

Have look at the "newbies read this" topic at the top of this section and you'll see that there is a lot of discussion around this.
I think it is important to remember that MFP has calculated a calorie deficit for you when you it calculates your calories for the day, so when you eat your exercise cals you still have enough of a deficit to lose weight.
Your body needs good fuel to function well, specially when you are exercising.

this is the best explanation I've read so far, well said.

Essentially, it is to ensure that you are losing gradually and not creating nutrition problems by burning more calories than you are eating. If you assume that your body needs a minimum of 1200 calories to just sit on the couch and survive, and then you burn 900 calories on the treadmill, then your body really only was fed a net of 300 calories. So, the argument goes that you want to keep your NET calories in the 1200 ballpark WHICH, by the way, has some weight loss already calculated in.

I think that this gets more important when you are burning LOTS of calories in a day. With no scientific support, I have usually don't eat back calories if lower than 200. From 300-600, I eat ~75% back. More than 700, I eat back about 50%. Ergo, I don't stuff myself when I am not hungry just to hit a net number. But, I do take in higher calories on days when I really burn a ton of calories.

You will hear a LOT of different answers on this one. Lots of opinions. Lots of VIOLENT DISAGREEMENT. So, please just consider this my humble opinion and the way I do it for me. Your approach may be different.

Cheers, Carter

I received really great advise from a person trainer on MFP. basically what she said was "Your body isn't going to go into starvation mode immediately. This will start to happen if you are eating WAY under 1200 calories a day for several days and exercising like a maniac." So basically what I do is listen to my body. I'm at a 1200 calorie deficit and I exercise almost everyday. I burn about 200-250 calories a day. Not a whole lot, but enough to keep my body going. I NORMALLY will not eat my calories back. 1 reason being I'm not hungry, 2nd because I don't feel that I need them. But every 3 or 4th day I will eat about 1400 calories. (eating back my exercise calories. This keeps my body going and it will not send my body into starvation mode storing the fat. This has worked for me. But this is only how I do it. Listen to your body. See how it feels, if it says eat, by all means eat. If it doesn't then don't.

As the posts before state that MFP already creates the cal defict and exercise is a negative cal input I try to eat most of those calories. However I do not always eat 100% of those calories, not because I want a bonus to weight loss but because I try to have a balanced healthy meal afterward. Since 1200 Cals are at the very least amount a female should be eating daily try to be very close to that goal to obtain the proper nutrition and to avoid putting your body into starvation mode. ( this can halt or even reverse weight loss. ). That is my two cents. Good luck with reaching your goals.