Basal Metabolism is the minimum amount of energy needed by
the body for maintenance of life when the person is at post absorptive state,
physical and emotional rest.
Basal Metabolic Rate (BMR) is a measure of the energy
required by the activities of resting tissue.
The Basal Metabolic rate can be measured directly from the
heat produced (using a Respiration Calorimeter and Metabolic Chamber) or
indirectly from O2 intake and CO2 expenditure when the
subject is at rest.
affecting Basal Metabolic Rate (BMR)
The factors affecting Basal
Metabolic Rate are listed in table-20B.
Factors affecting Basal Metabolic Rate
Body Compositon : The more lean body
mass higher is the BMR. This is due to greater metabolic activity in these
tissues when compared to bones and fat. Men with a high proportion of muscle
mass or lean body mass have a higher BMR than women.
Fever: Fever raises the BMR. There is a
7% increase in BMR for each degree rise in temperature in Fahrenheit.
Stress Smoking & Caffeine : Stress
raises BMR. Increases the BMR
Hyperthyroidism (Oversecretion thyroxin)
: The basal metabolic rate is elevated as of much as 50-70%.
Growth : In children and pregnant women
the BMR is higher.
Pregnancy : During the last trimester of
pregnancy Basal Metabolic rate is increased by 15- 25% as there is a increase
in muscle mass of uterus, size of mammary gland, foetal mass and placenta,
cardiac work and respiratory rate.
Fasting/Starvation : Lowers BMR
Hypothyroidism (under secretion of
thyroxin) : The basal metabolic ra
Age : Lean body mass diminishes with age
slowing the BMR. In tall people the BMR is higher.
Undernutrition : Prolonged undernutrition lowers the BMR.