Confused about minimum calorie consumption

Dear MFP community,

I am in desperate need for some help please!

I am a BodyMedia armband user and on a normal day in the office with my usual 30 minutes slow walk there and back [15 min each way] I burn around 1,800 to 1,900. I have worked out that my BMR is 1,470 and MFP suggests that I should be eating 1,340 a day, plus what ever extra I "earn" through exercise. I am worried that by only consuming 1,340 I would be under eating and my body would go into starvation mode and store all the fat rather than releasing it. I tried eating 1,400 on BodyMedia and didn't really lose that much weight. I am really confused!

What advise would you give me please? I am also aiming to go to the gym 2-3 times a week, working out for about 30 minutes. I'm really stuck with my weight and would like to get the ball rolling again.

I would really appreciate your help!

Many thanks.
Ankinha