i need some help understanding something

When you put in all your info and MFP gives you a calorie target, most people choose "sedentary" to get the lowest possible calorie count and also choose to lose 2 lbs/week. Well if you work out, you're not sedentary, and for some people, creating a 1000 calorie/day deficit just isn't all that realistic.

So if you choose "sedentary", you should eat back your exercise calories. If you choose a more active lifestyle quotient those calories are estimated and added in by MFP so you then don't have to eat your exercise calories.

If you're restricting to 2000 calories, you may not need to eat any exercise calories to lose weight safely. The rule of thumb is you should net a number of calories equal to or over your BMR daily.

If your BMR is 1800 calorie and you eat 2000 calorie and you burn less than 200 calories in exercise, you will net over 1800. If you eat 1900 but burn 300 you will net only 1600, which is below your BMR and may slow your metabolism down over time.

When people say you should eat back your exercise calories, I would suggest it is for highly active people i.e. athletes, or those with a calorie goal of 1200 calories/day (which is under most peoples' BMRs).

That probably is as clear as mud. Sorry 'bout that.

Okay to be exact instead of examples MFP tells me to be at 1700 calories. I can easily accomplish this. So my question is why exercise?

So you can eat more! (plus the multitude of health benefits)

Okay to be exact instead of examples MFP tells me to be at 1700 calories. I can easily accomplish this. So my question is why exercise?

True enough. You can lose all the weight you want by just dieting but exercise helps keep your metabolism up, and strength training specifically improves your body composition so that it's easier for you to lose weight and gives you the structure you want when the weight is off. Strength training also helps prevent muscle tissue loss when you're dropping pounds. Cardio is good for you. Strengthens your heart, lungs, and actually helps lower cholesterol as well. I do my cardio fasted in the morning so I think it helps persuade your body to let go of some of the fat. Opinions vary but I do have to say it's working wonderfully for me.

Personally I just add in about 200 - 250 for cardio and don't even bother logging calories burned for strength training. Of course my MFP goal is set above 2000 to begin with so I get to eat plenty during the day. Some people just enjoy the extra calories in their diet.