Metabolism is the sum of all chemical and physical processes in your body. All of these processes require energy which your body gets from stored supplies (body fat) and / or from food.
Some of these chemical and physical processes are essential for keeping you alive. This is called basal metabolism.
Basal metabolism is therefore the minimum amount of energy (calories) required for all life-important functions. In other words basal metabolism is the energy needed if you would sleep all day and not move a muscle. BMR is short for basal metabolic rate.
Basal metabolic rate
Despite what was said before about being in bed all day and not move a muscle, basal metabolic rate can represent a large portion of daily energy consumption for non active people.
Basal metabolism rate is the sum of following processes: respiration, blood flow, nervous shims, maintaining body temperature, normal functioning of the gastrointestinal tract, making new blood cells, hormones, etc..
Basal metabolism rate is also one of the key factors in how much food should we eat if we want to lose weight, gain weight or maintain weight. It is influenced by the following internal and external factors:
As with most other physical and physiological properties DNA has an important role with basal metabolism. Some people are born with a slower metabolism, others with a faster metabolism.
Men generally have more muscle mass and less body fat. This means that they also have a faster metabolism.
Basal metabolism rate decreases with age. After the age of 20 years your metabolism is reduced by approximately 2% for every 10 years.
Heavier people with more muscle mass have a higher basal metabolic rate.
This factor depends on the height and weight of your body. People with a bigger skin surface area have a higher basal metabolism rate.
People with a lower percentage of body fat have a higher basal metabolic rate.
Any restriction on caloric intake can result in a drop in basal metabolic rate. Composite diets may eventually reduce your BMR by 10% – 20%.
An increase in body temperature (eg due to illness) leads to an increase in basal metabolic rate. The rise in body temperature of 0.5 degrees Celsius can cause an increase in basal metabolism by about 7%. However, the changes are not linear; a patient with a body temperature of 42 degrees Celsium can have a BMR increased by up to 50%.
The exposure to a cold environment increases the basal metabolic rate, as your body must produce more heat to maintain the normal body temperature. Short-term exposure to hot environments does not effect basal metabolism because the changes are offset by faster heat dissipation. Longer exposure to heat may rise basal metabolic rate.
The increase in the level of certain hormones can have an impact on basal metabolic rate – BMR can increase. Among these are the T4, T3 (thyroid hormone) and adrenaline.
High-intensity exercise increases the rate of basal metabolism rate. However medium and low intensity exercise does not effect BMR. Exercise can increases metabolism indirectly aswell by building larger amout of muscle mass. Muscles are much more energy-consuming than the fatty tissue.