Calculating BMR and Daily Energy Expenditure
Resting Metabolic Rate (RMR) and Basal Metabolic Rate (BMR) are measures of resting energy expenditure, representing the minimum amount of energy required to keep your body functioning, including the heart, lungs and temperature regulation. Described here are equations for estimating BMR - see also information about the direct measure of BMR and RMR. By multiplying BMR by an activity factor, you can determine how many calories are required each day to maintain body weight based on your daily activity level.
- aim: to use formula to estimate metabolic rate at rest, and from that a daily energy expenditure.
- equipment required: calculator, and scales for weight and tape measure for height.
- procedure: See the procedures for height and weight. Use the formula below to determine BMR, and daily energy expenditure. If required, you can convert weights and lengths.
- BMR formula: The Harris-Benedict Equation has for a long time been the standard formula and is widely used for estimating BMR. Use the calculations below to calculate BMR, where: Wt = weight in kg, Ht = height in cm, A = age in years.
men: kcal/day = (13.75 x Wt) + (5 x Ht) - (6.76 x Age) + 66
women: kcal/day = (9.56 x Wt) + (1.85 x Ht) - (4.68 x Age) + 655
- Harris-Benedict Principle: Use the following table to calculate your recommended daily calorie intake to maintain current weight.
|Exercise Level||Details||Calorie Calculation (Daily Needs)|
|Little to no exercise||BMR x 1.2|
|Light exercise||1-3 days per week||BMR x 1.375|
|Moderate exercise||3-5 days per week||BMR x 1.55|
|Heavy exercise||6-7 days per week||BMR x 1.725|
|Very heavy exercise||twice per day, extra heavy workouts||BMR x 1.9|
- comments: The Harris-Benedict equation was first published in 1919. Since then there have been many other studies attempting to improve it, with limited success. Another commonly used equation for calculating RMR is the Mifflin equation.
- References: Harris JA, Benedict FG. A Biometric Study of Basal Metabolism in Man. Washington, DC: Carnegie Institute of Washington, 1919. Publication No. 279.