Does net really matter?

You should be eating so your net is your daily calorie goal without exercise.

Your daily goal is 1200 which you eat up to. You exercise and it burns 800 calories your net is only 400 calories if you don't eat any of your exercise calories back. Your body can't run on 400 calories for long. You need fuel for your body (much like gas in a car).

You should be eating more especially if you truly are burning 800-1000 calories in a day working out. Try to get that number at the top of your home screen as close to 0 as possible.

I eat mine back. If it a long run day where I burn 800-1600 extra I try and eat some back and then I know by the next day I will be able to eat the rest back.

Eat to your net goal.

^^^^ This

You don't want to consistently, or regularly, be eating too low. It simply isn't a case of "low is good.... so a lot lower is a lot better..." don't make this mistake.

Define "matter".
I think it matters.
I eat ALLLLLL mine back. upwards of 3000 calories a day sometimes.
Food is not the enemy. There is really no reason to be only be eating 1200 calories a day if you are truly burning 800+ calories a day.

The bigger question is how much do you care about your muscle? If you like muscle then you should eat them. Now consider if mfp is estimating then you should eat 50-75% of them. If its a hrm then 80%. The best thing is on days you know you are gonna workout, then eat more during the day. Or do what i do for all the people i help look at calories over the week. This way its easier to track.

I don't worry about net! On days when I have big workouts and burn 1000 calories then I try to eat between 1200-1500! Otherwise I try to stick as close to 1200 as possible unless I'm just super hungry! Hunger is a good sign as to whether or not you should eat more to make up for that! I try never to go over 1500 though!

Um, no. Hunger isn't a good sign of anything. Hunger is a hormonal response that changes based on your eating patterns. When you consistently under eat, your body adjusts to it, and you don't feel hungry. It's a survival instinct, as all your body knows is there is a serious lack of food available, and it takes a lot of calories to create the hormones necessary to signal hunger.

Eating 1200 calories and burning off 1000 exercising is the equivalent of eating 200 calories a day without the exercise.

If someone told you they were eating 200 calories a day, would you encourage them to keep doing it?