Glucose is the preferred immediate source of energy for our muscles. Brain and countless other specialized cells. Any carbohydrate can be broken down within a certain amount of time to create more glucose. But since glucose is corrosive when in the blood it gets converted and stored in the cells as a denser collection of glucose known as glycogen.
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Our muscles will use any readily available glucose first and then use its stores of glycogen. When insulin comes around to distribute glucose. Our cells use that energy. But also take enough glucose to replenish their stores of glycogen.
Insulins rather elegant system for storing toxic glucose in the muscle and liver doesnt function so well when the body is frequently exposed to high levels of blood glucose.
Frequent or prolonged spikes in blood glucose can cause the bodys cells to become resistant to insulin. If our blood sugar and insulin spike when our glycogen stores are mostly full and our cells energy requirements are low then the cell will not be receptive to any insulin because it doesnt need glucose. This leads to a resistance to insulin as the connections normally used to accept it begin changing and it becomes difficult for cells to accept insulin. Even if they really needed glucose.
Imagine insulin as a door-to-door Girl Scout selling cookies (glucose). When we first see those girl scouts we are craving cookies and we (muscle/liver cells) order as many as we can eat (glucose) and store (glycogen) and everything is fantastic. Now imagine you get your cookies and another girl scout comes to sell cookies. Well. Youre fully stocked on cookies. So maybe you buy just one box. Then. A day after that. Another girl scout comes and you just have to turn her away. Now. The poor girl scouts have too many cookies left to sell and they might get their sisters or parents (more insulin) to take some boxes around the neighborhood (high blood sugar) until they finally sell. In a sense. This is how insulin resistance begins. But it gets much worse from here.
As we mentioned before. Repeated levels of high insulin secretion were not normal for our prehistoric ancestors. The intended role of insulin in the body was to signal the muscles and other cells to fill up their depleted stores of glycogen and use the glucose available. When insulin was released. The cells usually needed that glucose and gladly opened up to receive the glucose. If we fill those stores and dont use them. Then when insulin comes to deliver some glucose those cells cant take in any more glucose and become resistant to insulin. The number of insulin receptor sites on the surface of the cells decrease in number as does their efficiency.
Blood glucose is increased as it has nowhere to go and the pancreas just sees that the levels of glucose in the blood are still too high and produces more insulin. What results is too much corrosive glucose persisting in the bloodstream as well as an excess of insulin. Which can cause problems of its own.
In a modern carbohydrate focused diet only serious endurance athletes can consistently deplete their glycogen stores to prevent this resistance. Even those who exercise still tend to overload their cells with glucose on a daily basis.
So. It might seem easy to just deplete those glycogen stores and you can eat more sugar. But it is not that simple. As cells repeatedly turn away insulin. They become used to doing that and begin to be less receptive to insulin even when they need glucose. So. even when cells need glucose they begin to need far more insulin than normal to be able to accept it causing insulin levels to routinely rise far more than a dose of carbohydrates should need.
Too much insulin can cause some problems. Especially when cells become resistant. Insulin will convert glucose to visceral fat as a last option. This fat surrounds the internal organs at first. And then grows around the abdomen. As fat grows by adipose cells accepting and converting glucose into fat. They can also reach a point where they have a difficult time accepting any more and become insulin.
With nowhere to go. The glucose usually ends up being converted to LDL cholesterol and wanders the blood. Clogging arteries.
As you can see. Insulin resistance can lead to an increase in both our blood glucose and insulin levels. Both of which have negative health consequences. But physical health can be affected – fat is easily accumulated and hard to lose, whereas muscle is difficult to gain and easy to lose.