Monday, 22 September 2008

Basal Metabolic Rate

from Wikipedia

Basal metabolic rate (BMR) is the amount of energy expended while at rest. BMR is measured under very restrictive circumstances when a person is awake, but at complete rest.

A more common and closely related measurement, used under less strict conditions, is resting metabolic rate (RMR).

About 70% of a human's total energy expenditure is due to the basal life processes within the organs of the body. About 20% of one's energy expenditure comes from physical activity and another 10% from thermogenesis, or digestion of food.

MD Mifflin and ST St Jeor in 1990 created the Mufflin equation for RMR:

  • For men: (10 x w) + (6.25 x h) - (5 x a) + 5
  • For women: (10 x w) + (6.25 x h) - (5 x a) - 161


w = weight in kg
h = height in cm
a = age
Example: crabsallover w=79.6kg (175.6 pounds/2.204 kg); h = 170cm (5'7"); a = 52. Hence RMR = (10 x 79.6) + (6.25 x 170) - (5 x 52) + 5
= 1603 (or 67 calories per hour)
Calculate your RMR.
The results of crabsallover calculations using the calculator are: BMR 1,661 RMR 1,605 (calories)
Factor Category Definition BMR RMR
1.2SedentaryLittle or no exercise and desk1,9931,926


1.375Lightly ActiveLight exercise or sports 1-32,2842,207

days a week

1.55Moderately ActiveModerate exercise or sports2,5752,488

3-5 days a week

1.725Very ActiveHard exercise or sports 6-72,8652,769

days a week

1.9Extremely ActiveHard daily exercise or sports3,1563,050

and physical job

For Crabsallover 1603 (RMR) x 1.375 = 2204 calories

Total Energy Expenditure (TEE)

So for a woman with a 1725 calories TEE, BMR would be 1208 (70%), Physical Activity 345 calories (20%) and 172 calories (10%) via thermogenesis.

From Caloriesperhour:-
  • When your age goes up, your BMR and RMR go down.
  • When your height goes down, your BMR and RMR go down.
  • When your weight goes down, your BMR and RMR go down.

This means that as you get older, shorter, and lose weight, your BMR and RMR will go down and you will need to eat less or exercise more to maintain your current weight. Oh my, it's tough getting old. At least as we get older we get wiser. Well, hopefully.

Using the Calculations

As BMR and RMR only represent resting energy expenditure, an adjustment must be made to reflect your activity level. This is done by multiplying your BMR or RMR by an activity factor (McArdle et al 1996). Note that the following activity factors also take into account The Thermic Effect of Food:

Activity Factor Category Definition
1.2 Sedentary Little or no exercise and desk job
1.375 Lightly Active Light exercise or sports 1-3 days a week
1.55 Moderately Active Moderate exercise or sports 3-5 days a week
1.725 Very Active Hard exercise or sports 6-7 days a week4
1.9 Extremely Active Hard daily exercise or sports and physical job

Use of these activity factors produces a very rough estimate, and there are many different opinions on what these activity factors should be. So again, we suggest that you calculate the actual activities that you perform as described in Calculating Daily Calorie Needs.

And when you do, note that calculations made with the Activity Calculator reflect the total number of calories burned during the period of time calculated. Therefore when calculating how many calories you need or burn in a day, do not add your BMR or RMR.

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