Cal allowed are already set for weight loss?

I posted this on a similar question last night:

MFP is designed around the idea of having a set calorie deficit. So if you're trying to lose 2 lbs/week, that's 1000 calorie deficit per day. MFP builds that deficit into your eating goals BEFORE any exercise is considered. So, to keep that same deficit, you are supposed to eat the additional calories earned through exercise.

Example:

Person A normally burns 2500 calories per day based on their height/weight/age/gender and normal daily activity level
So to lose 2 lbs/week, they need to eat 1500 calories/day (2500 - 1000 = 1500)

If they workout and burn 500 calories, then they've burned 2500 + 500 = 3000 calories. If they only eat 1500, their deficit will now be 1500 instead of the 1000 that is planned.

You may be thinking that a higher deficit is better, but that's not really the case. Slower weight loss is better - it is more likely to stay off, and it can ward off health problems from losing weight too fast. 2 lbs/week (1000 calorie deficit per day) is the highest amount recommended unless you're under doctor supervision.

SO to answer your question: YES you're supposed to eat those calories, especially if you're only on a base of 1200 per day. You need to keep your net calories (calories eaten minus exercise calories) at a high enough level to keep your metabolism from slowing down. If you eat low net calories for a long period of time consistently, then you will lower your metabolism and weight loss will be difficult.

That said, one day of not eating them won't hurt - just try not to do it regularly. When you know you'll be working out, plan ahead and eat a heavier lunch or breakfast. Also, you don't necessarily need to eat ALL of them - it's very easy to overestimate exercise calories (I find MFP tends to be pretty high estimates), and if you eat all of them, that can slow weight loss because you're decreasing your deficit. I aim to eat 50-75% of mine.