Do I have to burn 3500 every week?

No.

If you ate 1200 a day and did not even get out of bed you would lose weight.... the calorie deficit is already built in.

if you do any exercise, you're supposed to log it into your diary and then eat back those calories (most people eat back 50 - 75% because mfp tends to over estimate calories burned)

however... 1200 is actually too low for most people...... you probably set it to 2lbs a week?

how much weight are you planning to lose? this will affect how much you should aim to lose per week.

Approximately, 3500 calories equal 1 pound of fat. MFP will generate 1200 for those who do not exercise at all. You should select your activity level based on your lifestyle without exercise and set your weekly weight loss goal to something reasonable and eat back some of your exercise calories:

As a rule of thumb, the following weekly targets would give a balance between minimizing negative side effects and seeing a reasonable weekly weight loss:
More than 75 lbs: 2 lbs/week
40-75 lbs: 1.5 lbs/week
10-40 lbs: 1 lb/week
Less than 10 lbs: 0.5 lb/week

http://www.myfitnesspal.com/topics/show/819055-setting-your-calorie-and-macro-targets

http://www.myfitnesspal.com/topics/show/1080242-a-guide-to-get-you-started-on-your-path-to-sexypants

Yes I set it as 2 lbs per week because I have an event in three months that I really want to be slimmed down at least halfway for. I'm 150 and my long term weight loss goal (not the goal for the event) is 120. I'm 19 years old and 5'1", which may be why I don't need to many calories.

At 19 years old 150 pounds and 5'1 you need more than 1200 calories. If you exercise on top of only eating 1200 calories then you are going to end up not being able to maintain your diet and either causing yourself harm or quitting.

You set your weight loss goal too aggressively and as a result MFP told you the bare minimum it is willing to tell you which is 1200 (that is where it bottoms out it will never go lower).

You are supposed to set a reasonable weight loss goal based on your weight, which for you would be at most 1.5 pounds per week but 1 pound might be better, then if you exercise you are supposed to eat those calories back...meaning if you burned 190 going for a run then you would eat an extra 190 calories that day.

That said burning 190 calories for running for 5 miles seems like a huge underestimate (which is unusual I'm used to people overestimating). I'm pretty sure running for 5 miles you would burn more like 400 than 190.

Um...no. you will lose eating below maintainance even if you don't exercise.

I said one mile at 5 mph lol, not 5 miles. I would burn way more than 190. Haha, I'm not that slow! And no I really don't expect to look like that whatsoever but that phrase has kept me from giving up and I love it. c:

Oh 1 mile at 5 mile an hour, got it. Okay well that is running for 12 minutes in which case I think you are overestimating your calories burned which is more typical.

MFP suggests that I eat 1200 cals every day. But to lose a pound a week, do I have to eat 1200 cals a day just to function, and then burn an extra 3500 cals a week, just to lose a pound? I feel like this somehow isn't correct, because I run a mile at 5 mph and I only burn 190 cals. Man that's gonna be a lot of work lol, but I'll do it if I have to.

Not quite. You burn calories just by breathing and talking and brushing your teeth.

You start with your BMR, which is the calories you burn just by being a human being with working lungs and a heart. For you, that's 1500. Then you add your activity level on here - say 500 (this is from walking, talking, etc). So your total burn a day is an estimated 2000 calories (I don't know the actual number for you, I'm making one up). Now, if you eat 1200 calories a day, you're sitting at an 800 calorie deficit a day (5600 for the week, so almost two pounds a week). Then exercise goes on top of that deficit if you don't eat those calories back.

I really think you're being too aggressive. My goal is 1280 calories a day - but I'm fat, like I could probably hibernate for a while.

I recommend bumping it down to 1lb a week - a really realistic goal.

Good luck

edit: derp

Also, I set my goal for 1 lb a week and only recently changed it to two, and it still gave me 1200 cals. It wasn't because of setting too high of a goal (although I have set it quite high, but only recently). When I had it set at one lb it said 1200.

For MFP to be correct about that then your NEAT would have to be 500 calories above 1200 or only 1700. A 1700 NEAT for a 19 year old woman who is 5'1 and 150 pounds....I guess I can believe that if you are completely sedentary and a couch potatoe. So yeah, perhaps 1200 at 1 pound a week. Keep in mind though that is with ZERO exercise. As soon as you exercise you need to eat more.

The reason that MFP suggested the exact same number of calories for losing 1 pound a week as 2 pounds a week just underlines the fact that it is bottoming out and refusing to go below 1200.

As long as you NET 1200 calories a day that is probably fine.

It wouldn't be me that's overestimating, it would be my treadmill who tells me how many I burned lol. And to The Virgoddess, I said it was one mile at 5mph, not 5 miles.

Yup...it would be the treadmill overestimating. The result is the same though. Wasn't trying to place blame, was trying to point out that if you burned 190 calories in 12 minutes that means you were burning close to 1000 calories an hour which is just not going to happen for a 5'1'' woman.

When I, as a 6' tall man, ran a 6.2 mile race in 53 minutes I considered that to be about a 900 calorie burn.

The deficit is built in to your calorie goal. Click on the "Goals" tab and it will tell you your projected weight loss. If you burn calories then it wants you to eat them back. But because of underestimations in calories eaten and overestimation in calories burned I don't recommend eating back more than half your calories burned.

Approximately, 3500 calories equal 1 pound of fat. MFP will generate 1200 for those who do not exercise at all. You should select your activity level based on your lifestyle without exercise and set your weekly weight loss goal to something reasonable and eat back some of your exercise calories:

As a rule of thumb, the following weekly targets would give a balance between minimizing negative side effects and seeing a reasonable weekly weight loss:
More than 75 lbs: 2 lbs/week
40-75 lbs: 1.5 lbs/week
10-40 lbs: 1 lb/week
Less than 10 lbs: 0.5 lb/week

http://www.myfitnesspal.com/topics/show/819055-setting-your-calorie-and-macro-targets

http://www.myfitnesspal.com/topics/show/1080242-a-guide-to-get-you-started-on-your-path-to-sexypants

MFP does not set 1200 calories for people who do not exercise. Ignore this. OP 1,200 calories is the minimum MFP allows period. You decided to get more aggressive with your weight loss goal(going from 1 pound to 2pounds weight loss per week). Without getting into BMR and TDEE and what would make sense long term for your goal if you eat 1200 calories a day and exercise you will lose weight. Some muscle, some fat, and mostly water. And you'll feel miserable doing it. If this is what you want then it is your goal. If you want to go slower and learn more about what your body needs consider at least going to www.fat2fitradio.com and working through a BMR calculator. It takes 30 seconds to enter the information and less then 10 minutes to read the various methods and estimates for your caloric needs based on what input you provided. Hope this helps.