BASAL METABOLIC RATE / BMR

 

                               

BMR is the amount of energy expended while at rest. The release of energy in this state is sufficient for the vital function of the body i.e. heart, brain, lungs, kidneys, liver, etc. This BMR differs from person to person depending on gender, age, height, weight. Several prediction equations exists for BMR. Most notable was Harris-Benedict equation, which was created in 1919. He created two different equations for men and women.


              Men: BMR = 66 + (13.7 X wt in kg) + (5 X ht in cm) - (6.8 X age in years)


              Women: BMR = 655 + (9.6 X wt in kg) + (1.8 X ht in cm) - (4.7 X age in years)


His equation was the best prediction until recently, when MD Mifflin and ST St Jeor in 1990 created new equation:


               P = (9.99m + 6.25h - 4.92a + s) cal/day


Here P is the total heat production (BMR),
s is +5 for males and -161 for female,
m is for weight in kg (1kg = 2.2lb),
h is for height in cm (1inch = 2.54cm)(1foot = 12inch),
a is for age.


For example if we take a female, 25 year old, say her goal or present weight  is 68kg(refer to the conversion rates above), 178cm height , her BMR would be as follows.
(pls note that iam using the same female example for all the equations)


BMR from Harris-Benedict equation:


                 BMR = 655 + (9.6 X 68) + (1.8 X 178) - (4.7 X 25)


                          = 655 + 652.8 + 320.4 - 117.5


                          = 1510.7  i.e. app. 1511 cal


BMR from MD Mifflin and ST St Jeor equation:
Let us take the same values of the above female and check them.Here s is -161 for female and +5 for males.


                   P = (9.99(68) + 6.25(178) - 4.92(25) -161)


                      = 679.32 + 1112.5 - 123 - 161


                      = 1508 cal


These two equations calculate BMR using total body weight .Later came a equation which calculates BMR with lean body mass which is more accurate.
Katch-McArdle's formula which is based on lean body mass. Since this equation is based on persons lean body mass, this is more accurate than formulas based on total body weight.
Katch-McArdle's formula using lean body mass, since this formula is based on LBM its the same equation for male and female.



                        BMR(men & women) = 370 + (21.6 X lean mass in kg)


Lets see how to calculate the lean body mass,



LBM = 100 - (body fat % / 100) X weight in kg


Lets take the same female example from above,


         LBM = 100 - (30/100) X 68
                  = 52.4
(i took 30% since the female is 25 yrs old and suppose she is healthy,her % would be between 21%-30% (Pls refer to the rough body fat percentages from my 'LEAN BODY MASS PERCENTAGES' post), remember these are rough values. Consult your doctor for exact fat levels.)


Taking the above female example, lets calcutate BMR from Katch-McArdle's formula,



                                BMR = 370 + (21.6 X 52.4)


                                          = 1502 cal


Now we know our BMR values and in the next post lets calculate our calorie per day (cal/day) using activity levels. Since all these equations give approximately the same calorie value, calculate your BMR value using one of the equations.
Pls visit  my 'DAILY CALORIE CONSUMPTION USING ACTIVITY LEVELS' post to calculate your daily Calorie.