First, you need to know how many calories you burn in a typical day. If you want to maintain your weight, eat the same amount of calories that you burn in a day. If you want to lose weight, you must burn more calories than you eat. The only healthy way to do this is through diet (eating less) and exercise (burning more).
To lose one pound, you must burn 3,500 calories. Most experts agree that healthy weight loss is at a rate of 2 lbs per week. To do this, you need to burn 7,000 extra calories per week or 1,000 calories per day. With a combination of decreasing your calorie intake by 500 calories and increasing your exercise to burn 500 calories a day, this goal can be easily achieved.