Fundamentals of Food Technology

Factors affecting the BMR

There are many factors that determine the basal metabolic rate of an individual
Size
Since the heat loss in body is proportional to the skin surface, a tall and thin person has greater surface and thus higher basal metabolic rate compared to the short person. The body composition shows variations in energy use. With little fat deposition in the body the basal metabolic rate increases and thus a tall, thin person has higher rates of basal metabolism compared to a short fat man. Constant muscular activities of an athlete demand about 5 per cent more basal metabolic rate.

Sex

Sex also makes a variation in energy requirement. The metabolic rate of women is 6-10 per cent lower than that of men.
Growth period
During the growing period the basal metabolic rate and the energy requirement are increased. The highest BMR is during the first two years. After the growth period, especially after 25 years of age, there is a decline in energy requirement.


Endocrine glands: The thyroid gland exerts influence over energy requirements. Thyroid hyper activity will speed up basal
metabolism. The pituitary gland also increase the metabolic rate. If there is disturbance in adrenalin the BMR increases.



Nutritional status: During undernourishment the basal metabolic rate also declines to an extent of thirty per cent.
Pregnancy: During pregnancy the basal metabolic rate is increased by about 5 per cent during the first and second trimester and 12 per cent during the third trimester.


Sleep: During sleep the BMR is less than in the waking state. Sleep decreases BMR by 10 per cent.

Climate: Climatic conditions of the environment also affect the energy requirement. If the temperature falls below 140C the energy requirement increases.

Body temperature: Fever increases the BMR. Every one degree celsius increase in temperature increases BMR by 7 per cent.

Disease conditions: Disease like typhoid fever, medullary diseases and lymphatic leukaemia show an increases in the BMR

Physical activities: Physical activities half an hour before BMR measurement show high rates of BMR