What is Type II Diabetes?
This past weekend I was perusing through the magazines at the grocery store when I came across an article headlined by the following statement:
Myth: Diabetes is caused by sugar or carbs.
Fact: Fat, not carbs, is most important when managing diabetes.
If you choose not to read the remainder of this post, please know that this claim is absolutely false. I was blown away that this could be published in a nationally distributed magazine. Physiology is not an easy discipline to understand and people tend to latch on to ideas they hear regardless of where they are from. Why do you think mulit-level marketing schemes are so popular in the nutrition industry? Let me give you a quick rundown of how Type II Diabetes in manifests itself in the human body.
First we need to define Type II Diabetes (T2D). T2D can be defined as the body's resistance to the hormone insulin. Insulin is a hormone that is created in the pancreas and is released into the blood when we eat carbohydrates. Carbohydrates are broken down into the simple sugar glucose. Glucose then enters the bloodstream and is sent to our cells. In order to enter into our muscle cells where it is stored, it needs to get help from insulin. Insulin acts as a chaperone to get glucose out of the blood and into the muscle cell. Glucose uptake into muscle cells is a crucial element in understanding the mechanism behind T2D.
The process of glucose uptake is as follows:
- Insulin binds to a receptor on the cell membrane.
- This signals to the transporter protein GLUT-4 to translocate to the cell membrane and create a door for glucose to enter.
- Glucose enters through the GLUT-4 protein.
- Once in the cell, glucose undergoes a reaction facilitated by the enzyme hexokinase to create an end product of glucose-6-phosphate. This process costs the body 1 ATP.
- Once glucose has been converted to glucose-6-phosphate it is trapped in the muscle cell and can either be stored as glycogen or burned for energy.
An simplified way of understanding the process of getting glucose into the cell is to use the analogy of a party.
Glucose wants to go to an exclusive party at the muscle cell but to get in it needs a chaperone. The chaperone in this analogy is insulin. So insulin chaperones glucose to the muscle cell where it knocks on the door of the cell to signal to the doorman to let glucose in (Step 1 from above). The doorman is a transport protein called GLUT-4. When insulin knocks on the door of the cell, GLUT-4 translocates to the cell membrane to open the door for glucose to enter (Step 2). Glucose has now entered the muscle cell but before he can begin to party he has to pay his cover charge (Step 3). You may recall from science class that ATP is the energy currency of the body. The body pays a cover charge of 1 ATP. Once paid, glucose receives a wristband and now glucose doesn't want to leave because or it would be a waste of money. When glucose gets a wristband it changes the structure of the molecule and it is now called glucose-6-phosphate. The reaction to change glucose to glucose-6-phosphate is facilitated by an enzyme called hexokinase. Hexokinase is like the ticket seller who hands out the wristbands (Step 4). Glucose is now in the cell and has one of two fates. It can be stored as glycogen or burned for energy (Step 5).
Great. Awesome. Perfect. Now that we have a general understanding of glucose uptake we can now look at how diabetes is manifested in the body. Recall how we defined T2D above, the body's resistance to insulin. Resistance to insulin means that our bodies don't respond to insulin's signaling like we would expect it to. What would cause this? Muscle cells that are chronically high in glycogen stores. The party at the muscle cell is full and there is no vacancy. You may know that two risk factors for developing T2D are obesity and lack of physical activity. When you combine these two things with overconsumption of food, specifically carbohydrates, you become at an increased risk for developing T2D. Let's connect the dots.
- Exercise burns energy. High intensity exercise burns carbohydrates almost exclusively. Glycogen (the storage form of glucose in muscle cells) is used for energy to fuel the exercise. Exercise is a glycogen lowering activity.
- Lack of physical activity over time leads to a build up of glycogen in our muscle cells. When our cells become full of glycogen, it can't store any more because it has no room available.
So if our glycogen stores are full and we eat carbohydrates what happens to the glucose? This is where insulin resistance begins. Insulin chaperones glucose to the muscle cell that is full of glycogen. It knocks on the door but our doorman, GLUT-4, can't hear the knock because the party is too full. Insulin then has to get another molecule of insulin to create a louder knock in order to get glucose out of the blood and into the cell. When glycogen stores are chronically high and insulin has to keep working in overdrive, problems will occur. With enough abuse, the cells in the pancreas that produce insulin can shut down causing glucose to drastically build up in the blood. At this point, a diabetic patient would need to use exogenous insulin.
Technically the magazine isn't wrong by saying that it is a myth that sugar and carbs cause diabetes, but they aren't exactly correct on saying controlling fat is most important in controlling diabetes. While carbs aren't directly the cause of diabetes, they do play a huge role in the development. To claim that fat is most important in controlling diabetes is patently false. What's most important in controlling diabetes is increasing physical activity and controlling your calorie intake, specifically from carbohydrates. Diabetes can be controlled through monitoring carbohydrate intake and maintaining an active lifestyle. It is important for you to understand the basic concepts of certain aspects of nutrition and physiology so that you can spot false claims like the one made by this magazine. The more you know, the better off you will be to serve your goals.