AND . . . that darn BMR goes down with AGE. Darn it! Women need about 5 fewer calories a day every year. That doesn't sound like much, but it means that I, at 60, would need 150 calories fewer every day than someone my size who is 30. That amounts to over 15 pounds a year (in the strictest sense of 3500 calories being equal to a pound.) I know there is no perfect formula for losing a pound for every 3500 calories burned or not eaten, but that's the basic principle of eating less and moving more.
I think I can post this link - it's to a very good BMR calculator. Just enter your information and it will show your BMR - what your body needs just to live (like you are in a coma.) Then it shows a little farther down the page what your actual caloric needs are based on your activity level.
A huge loss at the beginning of a "diet" is usually due to losing a lot of water, too. That slows down in a very short while. I lost at the rate of about 3 pounds a week for the first 10 weeks. I used an Excel spreadsheet to record my actual loss against a projected loss that would get me at my goal in a certain amount of time. I charted it at 30 pounds for the first 10 weeks, but then changed it to 1% per week after that. At my starting weight that schedule puts me at 150 pounds the week before Christmas. BUT . . . I'm about 8.5 pounds ahead of schedule, so that allows for a slow down when it comes - I'm just about 21 pounds from my 152 pound goal. That is 100 pounds in 11 months + 1 week. I think it's doable and that 1% per week is a great rate to lose. Of course, I'm overjoyed when I see more than 1%! You'll learn as you continue this journey that all this said, some weeks are magic and some seem cursed! Just stay on plan as best you can and you'll see results.
Life style change started on Jan 13, 2011. I was going to lose 100 pounds by Christmas.
I lost 93 pounds by Oct 1, 2011 and am holding there for now. We'll see what happens.
New goal: To maintain at about 160
Final Goal: To decide if I need to lose more
Just Keep On Keepin' On