what is insulin sensitivity

What is Insulin Sensitivity

The term “insulin sensitivity” is thrown around a lot today by fitness and nutrition gurus. But what is insulin sensitivity?

Insulin sensitivity refers to how responsive tissue is to the hormone insulin. When a tissue is insulin sensitive it has a large nutrient storage response to a small amount of insulin. The opposite of insulin sensitivity is insulin insensitivity.  When a tissue is insulin insensitive a large amount of insulin only results in a small nutrient storage response. You see, when tissue such as muscle, is not insulin sensitive nutrients like carbohydrates and proteins stay in the bloodstream, rather than traveling into cells or tissues.  

Let’s further examine the hormone insulin to get a better understanding of what is insulin sensitivity. 

Insulin- “The Gatekeeper” Hormone

Insulin is a hormone that is synthesized in the pancreas by the beta cells and is secreted when blood sugar levels rise.  Insulin’s job is to allow nutrients into your skeletal muscle, liver, and fat cells. Without the presence of insulin, nutrients cannot enter the cell. Insulin is often called the “Gatekeeper” of the cell for this reason.  

Insulin After Eating a Meal…

Here is an example of how insulin functions after you eat something like a doughnut: sugars from the doughnut get broken down by the stomach and are absorbed by the small intestine and then enter the bloodstream. Sugars enter your circulation and are ready to be taken in by the cells to fuel processes like cellular respiration. Without insulin, the circulating blood sugar would never reach the cells and they would essentially starve.

Insulin’s Mechanism of Action in the Cell 

So how does insulin act as the “gatekeeper” and allow nutrients into the cell? When blood sugar levels rise the pancreas releases insulin into the bloodstream. Glucose can only enter into the cells after insulin has been bound to an insulin receptor on the cell membrane.  Once bound, a series of chemical reactions takes place within the cell. Eventually, this causes glucose transporter proteins (GLUT-4 proteins) to translocate to the cell membrane. Once these transporter proteins have been incorporated into the cell membrane, the glucose now has a “door” to come in through.  And hence, glucose enters into the cell.  

Glucose Storage

Once glucose has entered the cell, a few different things can happen:

  • Glucose can be used immediately to fuel cellular respiration to supply the body with energy.
  • Glucose can be stored in the liver and muscle as glycogen.  Glycogen, much like fat, is a stored form of chemical energy.  When your body needs energy, it serves as a fuel source.
  • Glucose can be transported into fat cells.  In the fat cells, glucose is converted into fatty acids via fatty acid synthesis. Fatty acid synthesis involves taking a glucose molecule (a 6 carbon ring molecule) and breaking it into two, 3-carbon pyruvate molecules. Subsequently, pyruvate gets transformed into acetyl CoA.  When energy demands aren’t high, acetyl CoA gets converted into triglycerides which are stored in the fat tissues. This is essentially how you pack on fat from eating loads of carbs.  

Insulin Sensitivity and Health

When it comes to your health, insulin sensitivity is extremely important. The more insulin sensitive your cells are, the better they are at removing blood sugar. When you are insulin insensitive, blood sugar levels stay elevated, and transport of the sugar into the cells is very inefficient. This is problematic because cells don’t get the energy they need to function properly. In addition, a myriad of other health problems start to progress like type 2 diabetes and heart disease.

The Blood Sugar “Traffic Jam”

When you are insulin insensitive, its like there is a traffic jam in your blood stream. Your blood stream is the highway and the molecules of sugar in your blood are like cars. When there is too many cars on the road you get traffic jams. This is very similar to how molecules of sugar act in the bloodstream when cells are insulin insensitive. What happens is glucose doesn’t get transported into the cells and remains in the bloodstream. Subsequently, a back up or “traffic jam” of glucose remains in the bloodstream and blood sugar levels rise.

Prolonged high blood sugar levels hurt you in 3 ways:

  • Increased Cravings– Your cells don’t get the energy they need to function because glucose isn’t entering the cells efficiently. As a result, cravings start to kick in even after eating a meal. Consequently, you end up snacking more, which elevates blood sugar levels even more.
  • You become even more insulin resistant– You eat, blood sugar levels rise, insulin gets secreted. Except each time insulin is secreted it becomes less and less effective at reducing blood sugar levels. Your insulin receptors get more and more desensitized with each large spike in blood sugar.
  • Muscle Loss– Insulin insensitivity eats away at muscle as well. Muscle building amino acids from the food you eat enter your blood stream but can’t get even reach the cells due to the “traffic jam” of glucose.

Interested in Becoming More Insulin Sensitive?

If you want to have less body fat and more muscle than becoming more insulin sensitive is key. If you are interested, check this link out here, which describes 9 different tactics for becoming more insulin sensitive. Good luck!

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