Harris–Benedict equation
The Harris–Benedict equation is a method used to estimate an individual's basal metabolic rate.
The estimated BMR value may be multiplied by a number that corresponds to the individual's activity level; the resulting number is the approximate daily kilocalorie intake to maintain current body weight.
The Harris–Benedict equation may be used to assist weight loss — by reducing kilocalorie intake number below the estimated maintenance intake of the equation.
Step 1 – Calculating the Harris–Benedict BMR
The original Harris–Benedict equations published in 1918 and 1919.| Sex | Units | Calculation |
| Men | Metric | BMR = 66.5 + + – |
| Men | Imperial | BMR = 66 + + – |
| Women | Metric | BMR = 655 + + – |
| Women | Imperial | BMR = 655 + + - |
The Harris–Benedict equations revised by Roza and Shizgal in 1984.
| Men | BMR = 88.362 + + - |
| Women | BMR = 447.593 + + - |
The 95% confidence range for men is ±213.0 kcal/day, and ±201.0 kcal/day for women.
The Harris–Benedict equations revised by Mifflin and St Jeor in 1990:
| Men | BMR = + - + 5 |
| Women | BMR = + - - 161 |
Step 2 – Determine Total Energy Expenditure
While the original paper does not attempt to translate BMR into total energy expenditure, a BMR result may be multiplied by a factor that approximates an individual's physical activity level to estimate their TEE. The following table enables approximation of an individual's daily TEE based on some example lifestyles.| Lifestyle | Example | PAL | Calculation |
| Sedentary or light activity | Office worker getting little or no exercise | 1.53 | BMR x 1.53 |
| Active or moderately active | Construction worker or person running one hour daily | 1.76 | BMR x 1.76 |
| Vigorously active | Agricultural worker or person swimming two hours daily | 2.25 | BMR x 2.25 |
History
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 1984 revision improved its accuracy. Mifflin et al. published an equation more predictive for modern lifestyles in 1990. Later work produced BMR estimators that accounted for lean body mass.Issues in dietary use
As the BMR equations do not attempt to take into account body composition, identical results can be calculated for a very muscular person, and a very fat person, who are both the same height, weight, age and gender. As muscle and fat require differing amounts of calories to maintain, the TEE estimates will not be accurate for such cases.The paper behind the latest update to the BMR formula states all participants in their study fall within the 'normal' and 'overweight' body mass index categories, and so the results also do not necessarily apply to those in the 'underweight' or 'obese' BMI categories.