Basal Metabolic Rate

What is Basal Metabolic Rate (BMR)?

Basal Metabolic Rate (BMR) is the amount of total energy expenditure necessary to maintain our basic bodies function under basal condition.

Basal condition means-

Person should be at rest.
Person should be awake.
Person should be without food for about 12 hours.
Person should be in a comfortable temperature (200-250C).
Importance of Basal Metabolic Rate:

Total daily calories requirement in our body = Basal Metabolic Rate + calories required for physical activity + calories required for food digestion.

So, Basal Metabolic Rate (BMR) is important to calculate the daily calorie requirement of a person and planning of diets.

The most useful way of measuring the total daily calories requirement is as a multiple of Basal Metabolic Rate (BMR). Sedentary workers use only 1.1 – 1.2 × BMR. By contrast, heavy workers may use 6 – 8 × BMR.

Calculation of BMR by Basal Metabolic Rate Formula:

Basal metabolic rate in male

= 66 + (6.23× weight in pound) + (12.7 × height in inches) – (6.8 × age in years).

or,

= 66 + (13.7 × weight in kilogram) + (5 × height in cm) – (6.8 × age in years).

Basal metabolic rate in female

= 655 + (4.35× weight in pound) + (4.7 × height in inches) – (4.7 × age in years).

or,

= 655 + (9.6× weight in kilogram) + (1.8 × height in cm) – (4.7 × age in years).

Average normal value of BMR is

In Male: 35-38 Kcal/m2 of body surface area/hour.

In Female: 32-35 Kcal/m2 of body surface area/hour.

Factors speed up the Basal Metabolic Rate:

Young age – BMR is high in young age because of young person contains more muscle tissue which is metabolically more active.
Male sex – BMR is high in male because of male’s bodies contain proportionally more muscle tissue.
More body surface area – BMR is high in person with more body surface area.
High or low environmental temperature – When the environmental temperature is higher than body temperature, BMR accelerated, and the metabolic rate increases about 14% for the elevation of each degree Celsius. When the environmental temperature is lower than body temperature, metabolic rate is increases through heat producing mechanisms such as shivering.
Pregnancy – BMR increase in pregnancy.
Emotional state – BMR increase in emotion.
Hormones – Thyroid hormone, testosterone, growth hormone, and catecholamine increases BMR.
Factors slow down the Basal Metabolic Rate:

Older age – BMR decrease in older age because of muscle tissue is replaced by fatty tissue in older age, which is metabolically less active.
Female sex – BMR is low in female because of female’s bodies contain proportionally more fatty tissue.
Less body surface area – BMR is low in person with less body surface area.
Starvation – metabolism will slow down in starvation for surviving the life.