Factors affecting metabolic rate

Not only physical activity level, but there are also other factors which affects metabolic rate are described below: 

a) Age: The metabolic rate for child’s are higher than the old people due to body growth. It is peak at 10 years of age. 

b) Exercise: Due to exercise metabolic rate increases dramatically. 

c) Body weight & surface area: Metabolic rate increases with the increase of weight & with the increase of skin surface area . 

d) Food consumption: Due to consumption of large quantity of food, metabolic rate starts increasing within 1 hour & continue about 3-12 hours.

 e) Sympathetic stimulation: Due to sudden reason metabolic rate may increase. 

f) Climate condition: Metabolic rate increases in cold weather & decreases in hot weather. 

g) Sleeping: During sleeping due to lowest physical activity level, metabolic rate reduces about 10%.

 h) Fever: The metabolic rate increases with fever. 

i) Malnutrition: In malnutrition, there is a paucity of necessity of food substances in the cell. The metabolic rate decreases upto 20-30%. 

j) Physical condition: The metabolic rate increases up to 10% for pregnancy & breast feeding. 

k) Heavy clothing: Due to wearing heavy clothing in cold weather or any other reason metabolic rate may increase upto 10-15%. 

 Physiology & body temperature:

  Human body always maintain constant core body temperature at 370C (98.60F) with ±0.50C tolerance under different climatic condition. 

 Due to any reason, any variation of body core temperature from 370C causes higher heat loss or heat gain to bring the body temperature back to 370C. 

 The core temperature 370C is called set-point. 

 Heat generation by human body is done by metabolic activity or oxidation of food. 

 Production of heat by human body can be partially controlled by controlling metabolic rate. Metabolic rate can be controlled by various physical activity levels. 

 If the core temperature varies more than ± 0.50C from the set point, mental state & physical operations are disturbed. 

 Due to higher variation of core temperature physiological disorder or even death may occur

The physiological response at different core temperature is mentioned below:

 When the body temperature falls, the respiratory activity automatically increases and generates more heat. The extreme symptom is shivering which can result five times increase in metabolic rate.

  Human body has separate heat & cold sensors. If both types of sensors provide signal of same magnitude we feel normal. If different, then we feel cold or warm. 

 With the increase in body temperature, blood vessels in the skin are expanded resulting more supply of blood to the skin surface. As a result skin temperature is increased & heat loss is increased. 

 In cold environment, blood vessels in the skin are squeezed resulting less blood circulation in the skin area hence less temperature loss.

  When the body core temperature is increased, the sweat gland in the skin are stimulated resulting in opening of the pores of the sweat glands and facilitates to pass body fluids (sweat). The evaporation of sweat causes body cooling. 

 Human body can tolerate or adjust at normal climate change but in extreme climate change like frost bite or heat stroke may happen in extreme cold & extreme hot condition. Even death may result if proper protective clothing is not worn.