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Harris benedict equation activity and stress factor

Harris Benedict equation – Determination of the basalmetabolic rate (BMR)

basal metabolic rate

Background

Basal Metabolic Rate (BMR)
Basal metabolic rate (BMR) is the amount of energy required tomaintain 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 noadditional activity. The energy consumed is sufficient only for thefunctioning of the vital organs such as the heart, lungs, nervoussystem, kidneys, liver, intestine, sex organs, muscles, and skin. 

Variance:
The resting and basal metabolic rate generally decrease with age orif there is a decline in lean body mass. Activities that tend toincrease muscle mass (lean tissue) such as body building or strengthtraining (anaerobic activities), will also increase the basal orresting metabolic rate. Aerobic activities such as running, skating,or rope jumping may improve endurance but have little effect on thebasal or resting metabolic rate (see post-exercise expenditurebelow). 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 normalfunctioning of one or more vital organs.

Lean tissue requires significantly more energy to maintain becauseof the increased level of metabolic activity. In contrast, fattissue requires very little energy to maintain and has littleinfluence 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 throughstrength training (corresponding increase in skeletal muscle), it ispossible to increase the overall basal energy requirements at rest.

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?

exercise

Sedentary.  Little to noregular exercise. 
(factor 1.2)

Mild activity level: Intensive exercise for at least 20 minutes 1 to 3 timesper week. This may include such things as bicycling, jogging, basketball,swimming, skating, etc.  If you do not exercise regularly, but you maintaina busy life style that requires you to walk frequently for long periods, youmeet the requirements of this level. 
(factor 1.375)

Moderate activity level: Intensive exercise for at least 30 to 60 minutes3 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 60minutes or greater 5 to 7 days per week (see sample activities above). Labor-intensive occupations also qualify for this level.  Labor-intensiveoccupations 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 trainingschedule with multiple training sessions throughout the day  (2) very demanding job, such as shoveling coal or working longhours on an assembly line. Generally, this level of activity is very difficult to achieve. (factor 1.9)

   

Background

Harris Benedict Equations:

BMR calculation for men (metric)
BMR = 66.47 + ( 13.75 x weight in kg ) + (5.003 x height in cm ) – ( 6.755 x age in years )

BMR calculation for women (metric)
BMR = 655.1 + ( 9.563 x weight in kg ) + (1.850 x height in cm ) – ( 4.676 x age in years )

Post-exercise energy expenditure: the amount of additionalenergy (above the resting or basal metabolic needs) expended after an activitydepends on the intensity and duration of the exercise session. More intensesessions tend to increase resting energy needs for longer time periods. Theseincreased energy requirements occur during the cool-down phase and areshort-lived. Sustained increases in the resting or basal metabolic rate can onlybe obtained through regular strength training routines that increase lean bodymass.

Summary:
Aerobic activity: short lived increases in RMR/BMR (cool-down period)
Anaerobic activity (regular): increases in lean body weight (LBW) –> Sustainedincreases in RMR/BMR.

Utilization


Utilization
: The baseline BMR or RMR can be used along withstress/activity factors to estimate the daily caloric needs of an individual – (Total EnergyExpenditure (TEE)  (kcal/day)).   See error rate below.

Total EnergyExpenditure (TEE)
The total energy expenditure (amount of calories needed per day) is composed ofthree primary factors: (1) Resting or basal metabolic rate   (2) Thermic effect of food  (3) Activities of daily living (ADL) – physicalactivity.

Thermic effect of food (TEF):
Rough estimation: TEF = Total calories consumed/day x 0.1
   Example: 2000 kcal diet.    TEF = 2000 x 0.1 = 200kcal/day.

TEF of protein >>carbohydrates>>fats.

Graphical representation:
total energy expenditure

Measurementversus 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 inmost cases. 
RMR:  less restrictive conditions and more easily obtained.  Theresting metabolic rate is only marginally different from the BMR.

Predictive equations:
An alternative method is to use predictive equations that can provide a roughestimate of the basal or resting metabolic rate.  The basal or theresting metabolism is the largest component of the total energy expenditure(TEE)…. usually 60 – 75%.  The RMR or BMR is usually at the higher end ofthis range for sedentary individuals (70-75%) and at lower the end for athletes. 

Error rate ofpredictive equations:

The various predictive equations for determining the resting or basal metabolicrates may significantly under or overestimate the total calories needed tomaintain the current weight of an individual when combined with stress/activityfactors that are selected by the user. This variance can approach 20% (over orunderestimation) depending on differences in  body composition (lean versusobese),  actual activity levels (athletic versus sedentary lifestyle), andenergy levels expended in thermogenesis.

 

Activity /Stress factors:

The following activity/stress factors when used along with an estimation of theresting or basal metabolic rate can be used to estimate an individual’s totalenergy expenditure (TEE) in kcal/day  (recommend daily calories to maintaincurrent weight = RMR + TEF + ADL). Sedentary.  Little to noexerciseDaily calories needed =
BMR x 1.2Mild activity level: Intensive exercise for at least 20 minutes 1 to 3 timesper week. This may include such things as bicycling, jogging, basketball,swimming, skating, etc.  If you do not exercise regularly, but you maintaina busy life style that requires you to walk frequently for long periods, youmeet the requirements of this level.Daily calories needed =
BMR x 1.3 – 1.375Moderate activity level: Intensive exercise for at least 30 to 60 minutes3 to 4 times per week. Any of the activities listed above will qualify. Daily calories needed =
BMR x 1.5 – 1.55Heavy or (Labor-intensive) activity level: Intensive exercise for 60minutes or greater 5 to 7 days per week (see sample activities above). Labor-intensive occupations also qualify for this level.  Labor-intensiveoccupations include construction work (brick laying, carpentry, general labor,etc.). Also farming, landscape worker or similar occupations. Daily calories needed =
BMR x 1.7Extreme level: Exceedingly activeand/or very demanding activities: Examples include:  athlete with an almost unstoppable trainingschedule with multiple training sessions throughout the day or a very demanding job, such as shoveling coal or working longhours on an assembly line. Generally, this level of activity is very difficult to achieve.Daily calories needed =
BMR x 1.9

Reference

BMR = 66.47 + ( 13.75 x weight in kg ) + ( 5.003 x height in cm ) – ( 6.755 x age in years )BMR = 655.1 + ( 9.563 x weight in kg ) + ( 1.850 x height in cm ) – ( 4.676 x age in years ): 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.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.: 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.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 0.1Example: 2000 kcal diet. TEF = 2000 x 0.1 = 200 kcal/day.TEF of protein >>carbohydrates>>fats.Graphical representation:: 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.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.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.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).

Harris JA, Benedict FG. A biometric study of human basal metabolism.Proc Natl Acad Sci USA 1918;4(12):370-3.

Basal Energy Expenditure:
Harris-Benedict Equation

Estimate basal energy expenditure using the Harris-Benedict equations.

  Male Female         Input Height cm in Input Weight kg lb Input Age yrs mos Stress Factor Activity Factor Bedrest Ambulating        

 

B.E.E. =   kcal/d Caloric Requirement  =   kcal/d

 

For men,
B.E.E. = 66.5 + (13.75 x kg) + (5.003 x cm) – (6.775 x age)

For women,
B.E.E. = 655.1 + (9.563 x kg) + (1.850 x cm) – (4.676 x age)

Total Caloric Requirements equal the B.E.E. multiplied by the sum of the stress and activity factors. Stress plus activity factors range from 1.2 to over 2.

  • Harris J, Benedict F. A biometric study of basal metabolism in man. Washington D.C. Carnegie Institute of Washington. 1919.

Special thanks to Dr. T.K. Shiao, University of Kansas Medical Center, co-author of Electronic Parenteral and Enteral Nutrition.

 

Created: March 9, 2000
Revised: October 3, 2000

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