Article # 361. Basal Energy Expenditure: Harris Benedict Equation

The Harris Benedict Equation is a formula that uses your BMR and then applies an activity factor to determine your total daily energy expenditure (calories). The only factor omitted by the Harris Benedict Equation is lean body mass. Remember, leaner bodies need more calories than less leaner ones. Therefore, this equation will be very accurate in all but the very muscular (will under-estimate calorie needs) and the very fat (will over-estimate calorie needs).

Harris Benedict Formula

To determine your total daily calorie needs, multiply your BMR by the appropriate activity factor, as follows: ·         If you are sedentary (little or no exercise) : Calorie-Calculation = BMR x 1.2 ·         If you are lightly active (light exercise/sports 1-3 days/week) : Calorie-Calculation = BMR x 1.375 ·         If you are moderatetely active (moderate exercise/sports 3-5 days/week) : Calorie-Calculation = BMR x 1.55 ·         If you are very active (hard exercise/sports 6-7 days a week) : Calorie-Calculation = BMR x 1.725 ·         If you are extra active (very hard exercise/sports & physical job or 2x training) : Calorie-Calculation = BMR x 1.9

Estimate basal energy expenditure using the Harris-Benedict equations.

Total Calorie Needs Example

If you are sedentary, multiply your BMR (1745) by 1.2 = 2094. This is the total number of calories you need in order to maintain your current weight.

Once you know the number of calories needed to maintain your weight, you can easily calculate the number of calories you need to eat in order to gain or lose weight:

Calculating the BMR

Early Harris-Benedict equations published in 1918 and 1919

Men: BMR = 66.4730 + (13.7516 x weight in kg) + (5.0033 x height in cm) – (6.7550 x age in years)

Women: BMR = 655.0955 + (9.5634 x weight in kg) + (1.8496 x height in cm) – (4.6756 x age in years)

Harris-Benedict Equation was reevaluated from the standpoint of resting energy requirements and the body cell mass. In 1984, Roza and Shizgal showed that resting energy expenditure is directly related to the size of body cell mass and is independent of age and sex. The variables in Harris-Benedict Equation reflect the relationship between body weight and the body cell mass.

Harris-Benedict equations revised by Roza and Shizgal

Men: BMR = 88.362 + (13.397 x weight in kg) + (4.799 x height in cm) - (5.677 x age in years)

Women: BMR = 447.593 + (9.247 x weight in kg) + (3.098 x height in cm) - (4.330 x age in years)

Once you know your BMR, you can calculate your Daily Calorie Needs based on your activity level using the Harris Benedict Equation.