You're asking the wrong question. :)
Basically, you adapt your amount of nutrition to the exercise you do; not the other way around. The vast majority of calories burned comes from daily living, exercise is added on top of that, and isn't the primary source of weight loss. It does make the process easier, and is necessary for overall health.
You will also find that weight loss slows the closer you get. The first 100 will come off faster than the last 50.
Here's what you do. Walk the amount that you want to walk for health; most doctors recommend 30 mins to an hour daily. This will improve cardiovascular health and get you moving. Then, do the math to figure out from there. 1200 to 1500 is not the amount someone with almost 200 lbs to lose you can lose on significantly more. I lost my first 20 lbs on 1700-2000, and that was only starting at 211!
Here's how SP calculates its ranges: www.sparkpeople.com/resource/nutrition_art
Writer, mother, wife, and breadwinner. I love to run, but running doesn't love me, so I'm switching to my low-impact bike.
I'm not pregnant, just fat: My blog. fatnotpregnant.blogspot.com/
| current weight: 186.4