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Basal Metabolism |
Most of the calories we burn daily do not derive from exercise or from the thermic effect of food, but rather from the automatic and largely unseen operations of our bodies that are collectively called "basal metabolism". It is the energy used to "mind the store" and it is substantial. The pie chart below illustrates the relative contributions of metabolism, exercise and thermic food effects to total calorie output in a typical human being. |
What IS Basal Metabolism? One way to define it is in terms of the information given in the pie chart above: your basal metabolic rate represents all the calories burned by your body in a day except those burned by exercise and digestion (thermic effect) of food. As the chart above illustrates, basal metabolism consumes the large majority of calories we burn in a day. But WHAT is it? What is happening to all those calories? Basal metabolism represents the total of all the metabolic processes of the body: heart beat, breathing, temperature regulation, thinking (yes, the brain consumes lots of calories during intense thought), cellular metabolism including cell division, repair, ion pumping, DNA, RNA and protein synthesis and far more. Basal metabolism is what keeps us alive. Can Basal Metabolism be Increased? Yes, it can and it is often. It is increased by infection for example. When a virus like the flu infects us, it hijacks our cellular metabolism and uses our own cells to make more viruses that in turn do the same thing to other cells in our body. This wastes calories (from our perspective but not from the virus' perspective). When our immune system begins to fight an infection, thousands of calories per day are shunted into antibody synthesis, into making white blood cells and to repairing the damage to our tissue caused by the virus and by our own immune system. Fever burns calories. So yes, metabolic rate can be increased. Can Basal Metabolism Be Increased in a Healthy Way? Yes. One way is to build more muscle. Muscle tissue has a much higher resting metabolic rate than adipose tissue (fat) and thus, the more muscle we have, the higher becomes our resting metabolism. Unfortunately, this effect is relatively small averaging about twenty extra calories burned per day per pound of muscle. Another way to increase resting metabolism is by making heat. Shivering, since it is an involuntary reflex, causes an increase in resting metabolism. Unfortunately shivering is unpleasant and stressful to the immune system. A better way to make heat is to have lots of "brown fat". That is a subject covered on another page. |
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