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
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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