PCOS and wieght loss

PCOS as a condition is generally accompanied by insulin resistance. It's the insulin resistance that is going to be your weight loss hurdle without the help of meds like Metformin. Insulin resistance will fight you every step of the way and makes it very difficult and in some cases extreme cases nearly impossible for you to manage you weight effectively, sans medication. I don't say this to be discouraging, just so you know what you're up against. You'll be fighting the way your system functions, on a very fundamental level.

To answer your question - MFP takes your weight/age/etc and calculates the base number of calories your body needs just to make it through the day. Then is subtracts a set amount, and makes that your calorie goal. (if you check the Goal page - you can see the calculation.) They are a little conservative, but generally, you want to eat as good portion of your exercise calories so that you aren't creating too much of a caloric deficit over the course of the day/week. Yes, it will mean that you're not going to lose a ton of weight in a short period of time, but it also means you will be giving your body the fuel it needs to continue functioning properly and power you through your workouts. A deficit of calories creates weight loss. Too much deficit leads to two things - first, you body will go into starvation mode - meaning it will hold out to EVERYTHING it can, which will lead to weight GAIN. Second, if you continue too long, your body will start cannibalizing your muscle for fuel. All in all, too few calories is almost as bad as too many. It's a balance that you have to strike.