Everyone's body works in a different way. For some it is easy to lose a few pounds and for others it can be close to impossible. Differences such as these can be attributed to our genes. Since we can't control the genes we have there is no sense in turning them into an excuse. If you have a difficult time getting rid of weight, then the solution is to work a little bit harder with your diet.
There's only one way to lose weight: creating a calorie deficit. You need to burn more calories than you eat over a prolonged period of time to see any weight loss. If you have a slower metabolism, you need to either eat less or burn more.
Your first step is to estimate how many calories you burn per day. The Calorie Calculator can help you with that. To lose 1 pound a week, you need to eat 500 calories less than you burn everyday. Double it to 1000 calories and you'll lose 2 pounds a week. Since the number you got with the calculator is only an estimate, it may take more than a week to actually see some weight loss.
After you figure out how many calories you need to burn and eat, you'll need to learn if these are the right numbers. Start off by weighing yourself at the begriming of the first week. Start your calorie restricted diet and weigh yourself again at the begriming of the second week.
At this point if your numbers were correct, you should have lost 1 or 2 pounds (depending on if you cut 500 or 1000 calories). If you haven't lost the correct amount of weight, cut an additional 200 calories out of your daily intake. Continue your diet for another week and weigh yourself again at the begriming of the third week. If you still haven't lost the right amount of weight, cut 100 calories out of your diet. You can continue this until you start losing weight (which shouldn't be too long).
You should never go under 1,200 calories a day since by the time you get to that level it'll be very hard for you to get all the vitamins and minerals you need. When you reduce calories to such a low level, your body can also go into starvation mode.
A starvation mode is your body's way of saving calories (by slowing down your metabolism) in preparation for a prolonged period of time with little or no food. If you are already at the 1,200-1,400 calorie per day level you should increase exercise to burn more calories instead of reducing your intake.
The Bottom Line
Remember that the weight didn't come on over a short period of time and it's not going to go away very quickly either. Weight loss requires dedication and patience so giving up after a week or two with little progress doesn't make sense.