It was the same with me and my guy. Its just a matter of burning more claories than you eat. Altho it is not recommended that you eat stupid low amounts of calories.
I have been dieting since christmas and have lost 28lbs (1 ans a half stone), this is through a combination of running (for an hour most nites) and eating sensibly and small amounts. Im plateauing at the moment
Anyways, good luck with your weight loss and I hope you find the forums as useful as I have.
x