Revised Harris Benedict equation - Determination of the
(BMR)
Background
Basal Metabolic Rate (BMR)
Basal metabolic rate (BMR) is the amount of energy required to
maintain the body's normal metabolic activity, such as respiration,
maintenance of body temperature (thermogenesis), and digestion.
Specifically, it is the amount of energy required at rest with no
additional activity. The energy consumed is sufficient only for the
functioning of the vital organs such as the heart, lungs, nervous
system, kidneys, liver, intestine, sex organs, muscles, and skin.
Variance:
The resting and basal metabolic rate generally decrease with age or
if there is a decline in lean body mass. Activities that tend to
increase muscle mass (lean tissue) such as body building or strength
training (anaerobic activities), will also increase the basal or
resting metabolic rate. Aerobic activities such as running, skating,
or rope jumping may improve endurance but have little effect on the
basal or resting metabolic rate (see post-exercise expenditure
below). Other factors that may affect the BMR or RMR include stress,
illness, hormone levels (e.g. thyroid), environmental (e.g.
temperature or altitude) or any other factor that effects the normal
functioning of one or more vital organs.
Lean tissue requires significantly more energy to maintain because
of the increased level of metabolic activity. In contrast, fat
tissue requires very little energy to maintain and has little
influence on the resting or basal metabolic energy needs.
Greater lean body mass = Greater BMR or RMR.
Because individuals can increase their total lean body mass through
strength training (corresponding increase in skeletal muscle), it is
possible to increase the overall basal energy requirements at rest.
Revised Harris Benedict equation:
(Revised: Roza et al.)
Age:
Gender:
Height:
Weight:
The activity level below will be used along with the BMR to calculate a
rough estimate of the number of calories needed per day (kcal/day)
Current daily activity level?
Sedentary. Little to no
regular exercise.
(factor 1.2)
Mild activity level: Intensive exercise for at least 20 minutes 1 to 3 times
per week. This may include such things as bicycling, jogging, basketball,
swimming, skating, etc. If you do not exercise regularly, but you maintain
a busy life style that requires you to walk frequently for long periods, you
meet the requirements of this level.
(factor 1.375)
Moderate activity level: Intensive exercise for at least 30 to 60 minutes
3 to 4 times per week. Any of the activities listed above will qualify.
(factor 1.55)
Heavy or (Labor-intensive) activity level: Intensive exercise for 60
minutes or greater 5 to 7 days per week (see sample activities above).
Labor-intensive occupations also qualify for this level. Labor-intensive
occupations include construction work (brick laying, carpentry, general labor,
etc.). Also farming, landscape worker or similar occupations.
(factor 1.7)
Extreme level: Exceedingly active and/or very demanding activities:
Examples include: (1) athlete with an almost unstoppable training
schedule with multiple training sessions throughout the day (2) very demanding job, such as shoveling coal or working long
hours on an assembly line. Generally, this level of activity is very difficult to achieve.
(factor 1.9)
Dieting - BMR - RMR
Calculators:
Several of these calculators may be particularly useful for dieters. Just
about every single MAJOR calorie/ energy equation that has been released
over the last 90 years is included below. Each calculator has a customized
printout option for easy analysis. Recommendation: Try each calculator -
print out the results - then compare!
Estimated 'Calorie' Calculators:
Harris-Benedict Equation:
Estimation of total calories needed. MOST widely used equation for calculating basal metabolic rate and total calories.
Revised Harris-Benedict Equation:The original Harris Benedict equation was revised in 1984. This updated equation can be used to calculate the basal metabolic rate and total calories.
RESTING Metabolic Rate (RMR):
Resting Metabolic Rate Calc - This equation can be used to calculate the RESTING metabolic rate and total calories. Mifflin-St Jeor equation.
Schofield equation (BMR)
:
This equation was part of the previous government guidelines to formulate RDA's and can be used to calculate the basal metabolic rate and total calories needed.
Institute of Medicine Equation- LATEST EQUATION:
IOM Equation-Estimated Energy Requirement (EER) Estimation of total calories needed. This equation is behind the 2005 Dietary Guidelines for Americans and the new food pyramid, MyPyramid.
Check out the new BMR multi-calc.
Background
(Revised) Harris Benedict Equations:
Note:
The original Harris Benedict equation was revised in 1984. This newer
equation may have greater accuracy in obese patients.
BMR calculation for men (metric)
BMR = 88.362 + ( 13.397 x weight in kg ) + ( 4.799 x height in cm ) - ( 5.677 x age in years )
BMR calculation for women (metric)
BMR = 447.593 + ( 9.247 x weight in kg ) + (
3.098 x height in cm ) - (4.330 x age in years )
Post-exercise energy expenditure: the amount of additional
energy (above the resting or basal metabolic needs) expended after an activity
depends on the intensity and duration of the exercise session. More intense
sessions tend to increase resting energy needs for longer time periods. These
increased energy requirements occur during the cool-down phase and are
short-lived. Sustained increases in the resting or basal metabolic rate can only
be obtained through regular strength training routines that increase lean body
mass.
Summary:
Aerobic activity: short lived increases in RMR/BMR (cool-down period)
Anaerobic activity (regular): increases in lean body weight (LBW) --> Sustained
increases in RMR/BMR.
Utilization
Utilization: The baseline BMR or RMR can be used along with
stress/activity factors to estimate the daily caloric needs of an individual - (Total Energy
Expenditure (TEE) (kcal/day)). See error rate below.
Total Energy
Expenditure (TEE)
The total energy expenditure (amount of calories needed per day) is composed of
three primary factors: (1) Resting or basal metabolic rate (2) Thermic effect of food (3) Activities of daily living (ADL) - physical
activity.
Thermic effect of food (TEF):
Rough estimation: TEF = Total calories consumed/day x 0.1
Example: 2000 kcal diet. TEF = 2000 x 0.1 = 200
kcal/day.
TEF of protein >>carbohydrates>>fats.
Graphical representation:
Measurement
versus predictive equations:
Direct measurement: Method: direct or indirect calorimetry.
BMR: Conditions: measured under very restrictive circumstances
and strict adherence to protocols. This method is generally impractical in
most cases.
RMR: less restrictive conditions and more easily obtained. The
resting metabolic rate is only marginally different from the BMR.
Predictive equations:
An alternative method is to use predictive equations that can provide a rough
estimate of the basal or resting metabolic rate. The basal or the
resting metabolism is the largest component of the total energy expenditure
(TEE).... usually 60 - 75%. The RMR or BMR is usually at the higher end of
this range for sedentary individuals (70-75%) and at lower the end for athletes.
Error rate of
predictive equations:
The various predictive equations for determining the resting or basal metabolic
rates may significantly under or overestimate the total calories needed to
maintain the current weight of an individual when combined with stress/activity
factors that are selected by the user. This variance can approach 20% (over or
underestimation) depending on differences in body composition (lean versus
obese), actual activity levels (athletic versus sedentary lifestyle), and
energy levels expended in thermogenesis.
Activity /
Stress factors:
The following activity/stress factors when used along with an estimation of the
resting or basal metabolic rate can be used to estimate an individual's total
energy expenditure (TEE) in kcal/day (recommend daily calories to maintain
current weight = RMR + TEF + ADL).
|
Sedentary. Little to no
exercise |
Daily calories needed =
BMR x 1.2 |
|
Mild activity level: Intensive exercise for at least 20 minutes 1 to 3 times
per week. This may include such things as bicycling, jogging, basketball,
swimming, skating, etc. If you do not exercise regularly, but you maintain
a busy life style that requires you to walk frequently for long periods, you
meet the requirements of this level. |
Daily calories needed =
BMR x 1.3 - 1.375 |
|
Moderate activity level: Intensive exercise for at least 30 to 60 minutes
3 to 4 times per week. Any of the activities listed above will qualify. |
Daily calories needed =
BMR x 1.5 - 1.55 |
|
Heavy or (Labor-intensive) activity level: Intensive exercise for 60
minutes or greater 5 to 7 days per week (see sample activities above).
Labor-intensive occupations also qualify for this level. Labor-intensive
occupations include construction work (brick laying, carpentry, general labor,
etc.). Also farming, landscape worker or similar occupations. |
Daily calories needed =
BMR x 1.7 |
|
Extreme level: Exceedingly active
and/or very demanding activities:
Examples include: athlete with an almost unstoppable training
schedule with multiple training sessions throughout the day or a very demanding job, such as shoveling coal or working long
hours on an assembly line. Generally, this level of activity is very difficult to achieve. |
Daily calories needed =
BMR x 1.9 |
Reference
Roza AM, Shizgal HM. The Harris Benedict equation reevaluated: resting energy
requirements and the body cell mass. Am J Clin Nutr July 1984 vol.40(1),168-182.
https://www.ajcn.org/content/40/1/168
Comment:
Miller, B; Merk, S; Bargi, U; Diem, P (2001). "Calculating the basal
metabolic rate in severe and morbid obesity". Praxis (Bern 1994) 90 (45):
1955-63.
Link:
https://www.ncbi.nlm.nih.gov/pubmed/11817239
(The revised equation may be more accurate in obese patients).
