What is the Harris Benedict Equation?

The Harris–Benedict equation (also called the Harris-Benedict principle) is a method used to calculate your total daily calorie expenditure by adding your activity level to your basal metabolic rate. When you use the Harris Benedict Equation you take your BMR value and multiply it by a number that corresponds to your activity level. The number that results from multiplying your BMR to your activity level is your recommended daily calorie intake to maintain your current body weight. The Harris-Benedict equation is used to assist weight gain or weight loss. By reducing your calorie intake number below the estimated maintenance intake of the equation. Below is a calculator that calculates both your BMR and incorporates the Harris Benedict Equation by adding a field for your activity factor. The body weight calculator below also takes into account your weight goal.

Harris Benedict Equation Activity Factor

In order to determine your total daily calorie expenditure you should add your activity factor to your BMR. Depending on how active you will want to add a different multiplier depending on your activity factor. Below is a chart outlining your activity factor multiplier, this is the number used in the harris benedict formula.

  • Little to no exercise
    Your calorie need = BMR x 1.2
  • Light exercise (1–3 days per week)
    Your calorie need = BMR x 1.375
  • Moderate exercise (3–5 days per week)
    Your calorie need = BMR x 1.55
  • Heavy exercise (6–7 days per week)
    Your calorie need = BMR x 1.725
  • Very heavy exercise (twice per day, extra heavy workouts)
    Your calorie need = BMR x 1.9

Harris Benedict Equation History

The Harris-Benedict formula was first published in 1919 when the first studies of human basal metabolism were conducted at the Nutrition Laboratory of the Carnegie Institution of Washington in Boston, Mass, under the direction of Francis G. Benedict. Prediction equations for basal energy expenditure (BEE) were developed from these studies. The expressed purpose of these equations was to establish normal standards to serve as a benchmark for comparison with BEE of persons with various disease states such as diabetes, thyroid, and other febrile diseases. The Harris-Benedict equations remain the most common method for calculating BEE for clinical and research purposes. A review of the data reveals that the methods and conclusions of Harris and Benedict appear valid and reasonable, albeit not error free. All of the variables used in the equations have a sound physiologic basis for use in predicting BEE. Supplemental data from the Nutrition Laboratory indicates that the original equations can be applied over a wide range of age and body types. The commonly held assumption that the Harris-Benedict equations overestimate BEE in obese persons may not be true for persons who are moderately obese.

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Andy is a weight lifting enthusiast with a passion for nutrition. He lives in the bay area with his family.

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