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INSULIN
Insulin is a storage hormone secreted by the pancreas. Its primary purpose
is to convert blood glucose into a form suitable for storage within the body.
When kept at optimum levels blood glucose is used as fuel for the body and stored
in muscle tissue for the synthesis of protein. Excess glucose is stored in the
adipose tissue as glycerol 3-phosphate which is used for the synthesis of triglycerols
(fat). It is therefore vital that optimum blood glucose levels are maintained
if you want to build muscle and decrease body fat.
Blood glucose levels are controlled primarily by the liver. Following a meal
high in carbohydrates blood glucose levels are dramatically increased. This
stimulates the secretion of insulin by the pancreas. In response the glucose
receptor sites in the liver are activated by the presence of glucose 6-phosphate
which allows for the uptake of glucose into the muscle and adipose tissue where
it is stored as glycogen. Once stored, blood glucose levels are decreased.
Insulin plays a directly anabolic role by facilitating the entry of amino acids
from digested protein into muscle tissue. Amino acids are the building blocks
of protein and are therefore vital for the building of muscle tissue. Insulin
also stimulates the production of somatomedins by the liver which are muscle-growth
factors, however, it is important to note that this involves insulin efficiency
not insulin amount as the amount of insulin that can be utilised by the muscles
is limited. Increasing insulin amount beyond an optimum level simply results
in the storage of any excess as body fat. Chromium facilitates insulin function,
therefore, in order to increase insulin efficiency sufficient chromium must
be present in the body.
Insulin does not work alone in promoting muscle growth, it works in synergy
with other hormones such as Growth Hormone. Most of the Growth Hormone produced
by the body travels to the liver where it is destroyed, however, before it is
destroyed it stimulates the production of Insulin-like Growth Factor I (IGF-I)
which is used in the muscle cells to stimulate growth. Your level of IGF-I and
your rate of muscle growth are therefore directly dependent on your insulin
supply.
In order to maintain a steady stream of insulin without producing excess it
is necessary to eat every few hours. Complex-carbohydrates are best as they
take longer to be absorbed and ensure a slow trickle of glucose into the bloodstream
preventing unnecessary peaks of excess which are ultimately stored as fat.
The exception to this rule is eating post-exercise. During intense training
your muscle tissue loses glycogen, the stored form of glucose, rapidly. When
blood glucose is decreased insulin production is also decreased and hence the
anabolic effects of insulin are hindered. The amino acids necessary for protein
synthesis and muscle growth can no longer be pushed into the muscle tissue and
IGF-I cannot be synthesised. In this scenario the body requires a quick ingestion
of simple sugar to raise blood glucose levels and stimulate the insulin drive.
It is also possible to boost the body's insulin supply by including amino acids
in your post exercise meal. Arginine and its precursor Ornithine increase insulin
levels and levels of Glutamine are correlated with muscle protein synthesis.
More and more research is being done into the anabolic effects of this very
powerful hormone. Understanding insulin and utilising it correctly to serve
you in your purpose to gain muscle and lose bodyfat is essential. Please refer
to the section on the insulin index for further information.
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