BMR

• Even breathing causes your body to burn calories. The amount of calories that your body needs just to exist is considered your BMR. Generally this accounts for 60 to 70 percent of your total daily energy expenditure (TDEE).
  
  

Thermic Effect of Food

• Your body burns calories processing the food you eat. The calories burned from biting, chewing, swallowing and digesting are considered to be a result of the thermic effect of food and account for about 10 percent of your TDEE.
  
  

Activity Level

• Your activity level is an important factor in determining how many calories your body burns. This may account for 15 to 50 percent of your TDEE. Use the Harris Benedict Equation (see resources) to help you determine your caloric expenditure.
  
  

Harris Benedict Equation

• Using the Harris Benedict Equation, a sedentary person would multiply his BMR by 1.2 to estimate the amount of calories burned from daily activities, such as yard work, driving and sitting. But someone who exercises vigorously would multiply his BMR by 1.9.
  
  

Putting it Together

• A 150-pound woman would burn about 2,080 calories per day. About 1,500 of these would account for her BMR, 150 calories for the thermic effect and the other 400 calories for her activity level.