Do you know how many calories your body burns in a day? That is a very important thing to know if your goal is to lose weight. In order to lose even one pound you must create a 3500 calorie deficit. This can be very difficult to do if you are unaware of your BMR, your basil metabolic rate. BMR is the number of calories your body burns in a day and can change depending on your weight, height, age and sex. As you lose weight your BMR changes and the number of calories it takes to continue to lose weight also changes. If it takes someone 1800 calories to maintain their current weight, and that person reduces their calories by 800 a day that person can expect to lose one pound in approximately 4 days or 2 pounds a week if they do nothing else but lower their calories. If the same person were to do a little extra physical activity each day then these results could increased.