Do i need to eat back the calories i exercise?

So my burn thingy says i burn 1800 calories a day sedentry. I aim to eat 1200 cals a day, and i burn atleast 300 calories. Do i need to eat back these calories?

At minimum, you shouldn't let your deficit (difference between total burned and total consumed) be greater than 1000 calories. So if you are burning 1800 sedentary, plus 300 in exercise, that's 2100 total burned, and eating 1200 gives you a 900 cal deficit.

So, in theory, you are ok. HOWEVER, many people on this site have found that it's better to keep to only 500 cal deficit, to keep your metabolism running - you still lose a pound a week, which ain't shabby. So you might want to consider eating 1600 calories.

thanks for posting this, im also confused about this 

i burn 1900 cals a day and am aiming at eating 1300 a day, i burn 700 a day running and am finding that my deficit is usually between 600-850. does anyone else usually keep a deficit of more than 500 or is this unsafe?

"Eating back" is one way of conceptualizing it, but it's more helpful to think in terms of total deficits than in terms of separating diet and exercise deficits.

 Since there's no difference in the weight loss between a calorie deficit created solely through diet and one created through diet and exercise it's a bit unhelpful to think of exercise deficits as separate from diet deficits. You have a daily calorie burn which includes your regular burn and potentially your exercise burn, and at the end of the day your goal is to have a calorie deficit that's within the limits of what your body can mobilise from fat stores.

 Since that limit is 31kcal/lbs fat mass/day your potentially useful calorie deficit varies with your body fat - with 10lbs of fat your max deficit is 310kcal/day, with 100lbs of fat it's more generous.

 There's also significant healt benefits associated with exercise and the National Weight Control registry longitudinal study has shown that one of the predictors of long-term success is regular exercise, something like 80-90% of the people who don't exercise on a regular basis regain all of their weight within 5 years.

 So it's possible to lose and maintain without exercise, but you're a statistical outlier when you do.

  It's difficult to predict exactly what your optimum deficit will be - the maximum is very seldom optimal for reasons that range from psychological to hormonal; out on the bleeding edge of what your body can cope with you're far more susceptible to stress-related illnesses and lowered immune system respone among other things, so in general it's better to have a deficit that's not somewhere up near your theoretical absolute maximum.

Everyone has told me to keep it around 500 to 600 deficit.  Anything less and it is believed that your body will do the starvation mode and try to conserve energy.  I don't know for sure - I am a newbe here!  However,  I am going by those guidelines and also letting my body tell me what it needs.  If I am hungry and I have a deficit of 700 - then I figure I need to eat.  But I am not willing to go under a 500 deficit.  It is working for me, so far, I'm loosing weight at a nice clip.  Also reading the educational posts by the founders - it seems that plateaus could be because of too large a deficit.   Anyway, interesting post.  I have also wondered if I need to eat more with exercise. 

no dont eat them back, those 300 calories u burned is burned fat. thats a good thing keep it up 

A lot of people have said good things in here.  Deficits are typically between 500-1000 calories in general.  Your body also gets used to a deficit after a while, so sometimes it's good to have higher or lower deficits to keep your metabolism up. 

And just because you burned 300 calories does not mean it's all fat.  I find that after I do harder workouts, I am more hungry.  If I don't eat it then, I wind up eating even more later and messing up my deficit.  You'll have to figure out what works best for your body.  If not eating it means you wind up grabbing crap later, then I'd eat it back. 

Thanks for all the replys everyone, i guess it's something that might take some time to figure out... I'll just listen to what my body tells me

exactly! only eat if you're hungry. if your body's telling you that you need more food/energy/calories, then by all means, eat...but if not, I wouldn't worry about it!