Some help understanding how I can shed weight?

Beksc_

I have started exercising about 2 weeks ago - prior to that I was sitting on the couch eating fatty foods and just completely letting myself go. Any time in the past that I have tried to lose weight I have put myself under extreme pressure, weighing myself constantly and hardly eating a thing.

This time I have weighed myself, taken my measurements and will not do this again until I hit the 6 week mark. I am 170cm and 86kg.

I am looking for help in understanding nutrition and how much I should eat and exercise. I have a desk job, so I do not naturally burn calories at work. I work out 5 times a week for 40 minute sessions, probably 30 mins cardio and 10 mins strength. With this information, I am told that I should eat 1,200 calories a day. With MFP, my calorie limit will increase when I exercise, but if I ate back those calories that I have just worked off, wouldn't I just maintain my weight, not lose it? Also, I have looked up my BMR - my expenditure is 1670 calories a day - surely this could not be right if I need to consume that many calories in order for me to stay alive?!?

Can someone please help me out, I am feeling really confused and I want to lose weight but not be light-headed and hungry all the time - basically I just want to be healthy so any advice would be great