The Harris-Benedict equation (also called the Harris-Benedict principle) is a method used to estimate the daily calorie requirements of an individual using their basal metabolic rate or BMR.[1] The estimated value is then multiplied by a number that corresponds to the person's activity level. The resulting number is the recommended daily calorie intake to maintain current weight. The equation does not take into account calories burned by existing large amounts of muscle mass, nor does it account for the additional calories provided by excess body fat—so the equation is more effective for individuals at an ideal body weight or close to it.[2]
The Harris-Benedict equation may be used to assist weight loss — by reducing the calorie intake to a number below the outcome of the equation.
Contents |
The following table enables calculation of an individuals Basal Metabolic Rate (BMR).
| BMR calculation for men | BMR = 66.5 + ( 13.75 x weight in kg ) + ( 5.003 x height in cm ) – ( 6.775 x age in years ) |
| BMR calculation for men | BMR = 66 + ( 6.23 x weight in pounds ) + ( 12.7 x height in inches ) – ( 6.76 x age in years ) |
| BMR calculation for women | BMR = 655.1 + ( 9.563 x weight in kg ) + ( 1.850 x height in cm ) – ( 4.676 x age in years ) |
| BMR calculation for women | BMR = 655 + ( 4.35 x weight in pounds ) + ( 4.7 x height in inches ) – ( 4.7 x age in years ) |
The following table enables calculation of an individuals recommended daily calorie intake to maintain current weight:
| Little to no exercise | Daily calories needed = BMR x 1.2 |
| Light exercise (1–3 days per week) | Daily calories needed = BMR x 1.375 |
| Moderate exercise (3–5 days per week) | Daily calories needed = BMR x 1.55 |
| Heavy exercise (6–7 days per week) | Daily calories needed = BMR x 1.725 |
| Very heavy exercise (twice per day, extra heavy workouts) | Daily calories needed = BMR x 1.9 |
Using the formulae above, a 24-year-old, 80 kg male who is 180 cm would have a BMR of 1900. If he exercised moderately, he would multiply his BMR by his activity level (1900 x 1.55) to determine daily calorie requirements, which would be 2945 kcal per day to keep his weight at 80 kg. This may seem like a high calorie intake, but his activity level requires it. This individual would exercise normally but not lose weight. The same individual without the exercise routine would only be able to consume 2273 kcal per day without gaining weight. The US Department of Health and Human Services Daily Value Guidelines provides figures that support the above example.[3]
Using the Harris-Benedict Equation, individuals can take a mathematical approach to weight loss. There are 3500 calories in 1 lb (0.45 kg) of body fat. Using the Harris-Benedict Principle, if someone has a daily allowance of 2500 calories, but he reduces his intake to 2000, then the calculations show a 1 pound loss every 7 days.
The Harris-Benedict equation sprang from a study by James Arthur Harris and Francis Gano Benedict, which was published in 1919 by the Carnegie Institution of Washington in the monograph “A Biometric Study Of Basal Metabolism In Man”.