It takes 3,500 calories to burn one pound. You can lose that pound through a combination of decreasing caloric intake to a healthy level and expending calories through physical activity.
- For example, if you currently take in 2,000 calories a day and decreased that by 300 calories a day (one slice of pizza) and added in 200 calories worth of exercise a day (20 minute walk), you would be at a 500 calorie deficit.
At that rate you would burn one pound a week. So eating 300 less calories a day and expending 200 calories a day through activity will result in a net of one pound lost per week. Obviously you could increase your activity and accelerate your weight loss. Check with your doctor to see if it is safe for you to accelerate your weight loss through decreasing calories.