How To Estimate Calories Needed In Addition To Bmr

Your basal metabolic rate, or BMR, determines the amount of calories your body expends performing all of its basic vital functions at complete rest. Your BMR, however, does not take into account your physical activity level. To factor in the number of calories typically burned through physical activity, researchers James Harris and Francis Benedict developed a formula based on several levels of exercise. You can use this formula to estimate the calories you need to consume each day, as well as the number you need to either gain or lose weight (see reference 4).

Step 1

Calculate your BMR. Men should use the formula: BMR = 66 + (6.23 x weight in lbs.) + (12.7 x height in inches) - (6.76 x age in years). Women can use the formula: BMR = 655 + (4.35 x weight in lbs.) + (4.7 x height in inches) - (4.7 x age in years).

Step 2

Apply the Harris-Benedict equation to your BMR to estimate your total daily caloric requirements. Multiply your BMR by the number 1.2 if you are sedentary, 1.375 if you exercise one to three days per week, 1.55 if you exercise three to five days per week, 1.725 if you exercise six to seven days per week and 1.9 if you exercise multiple times each day.

Step 3

Calculate the number of calories you need from each macronutrient. According to the Food and Nutrition Board of the Institute of Medicine, adults should consume between 45 and 65 percent of their calories from carbohydrates, 20 and 35 percent from fat and 10 and 35 percent from protein.

Step 4

Calculate the number of calories you need to gain or lose weight. To either gain or lose 1 lb. of body weight, you need to consume either 3,500 calories more or less than your body requires over time. You can therefore gain or lose about 1 lb. each week by obtaining a daily surplus or deficit of 500 calories per day.