Your basal metabolic rate is the amount of energy you burn while your body is at rest in a neutrally temperature environment. This occurs during the periods while you are fasting and your digestive system is inactive. For example, if you decided to fast for a day and sit around and watch television all day, your body would burn a certain amount of calories just to keep you awake and your organs functioning. Granted this isn’t a very healthy approach and should not be considered when needing to drop a few pounds. As you get older your BMR decreases as well as when you lose lean muscle mass, but if you exercise and increase your lean muscle mass your BMR actually increases, therefor burning more calories per day.
The primary organ that is responsible for your metabolism is your hypothalamus. Your hypothalamus is location in the diencephalon region of the brain (relevant? No but fun fact!). The hypothalamus controls the activities of our autonomic nervous system (ANS). This system controls our smooth muscle contractions of the heart, GI tract movement, as well as the movement of the lungs and bladder. Autonomic means automatic which states that we don’t need to think about these certain actions that take place within the body because our brain automatically communicates to the rest of the body to do so. The ANS also helps regulate the temperature of our body which is the reason for our boy’s natural response to sweat and shiver in different temperatures.
For our BMR most of our energy is expended by maintaining fluid levels in the tissue through osmoregulation and about 10% is used for mechanical by work by our ANS such as digestion, heart beating, breathing, etc. Therefore, the more lean muscle mass you have the more the body needs to maintain proper metabolic balance within that tissue.
Our body’s Krebs Cycle requires energy to perform metabolic changes through the foods we consume through fats, carbohydrates, and proteins. With muscle contraction our body undergoes an exergonic transfer of energy to allow endergonic reactions anabolic reactions to allow the muscles to contract. This basically means that our body allows the breakdown as well as a buildup of energy that is associated with muscle contraction. The molecule that is responsible for this process is ATP. The breaking and building of these chemical bonds of ATP is what provides the Krebs Cycle to work.
Over all, the activity occurring in our brain, which is controlled by our ANS, which monitors our fluid retention in our tissue to the energy system needed to contract muscle, all of these factors work together to form our BMR. Even though we are at rest, our bodies are going through so much and still require energy to perform and function.
*** If you want to see what your BMI is then click here