Insulin is a hormone produced by the pancreas that signals cells to extract glucose (blood sugar) from the blood. Some people mistakenly think that insulin actually participates in the action of glucose uptake. But, as a hormone, it simply signals the cells to take action. The actual glucose uptake is up to those cells. In fact, in some cases, glucose uptake can occur without insulin. The best example is with muscle cells during exercises, where cells can sometimes extract blood sugar without being signaled. But, in general, insulin is required to trigger this action.
In diabetes, this action is broken. In a small percent of diabetics, the problem is because the pancreas cannot produce any insulin. This is referred to as type I diabetes. Far more common, however, is type II diabetes. Type II diabetes is reaching epidemic proportions in the US. At least initially, type II diabetes is not a condition of the pancreas and insulin production. Indeed, at least initially, type II diabetics produce considerably more insulin than a non-diabetic.
Type II diabetes is a disease of insulin resistance, where insulin is produced but the cells do not respond sufficiently to it. In most cases, this results in more and more insulin being produced to compensate until eventually it is not possible to keep up. This is the point where diabetes can be diagnosed.
Diabetes causes two primary problems. First, the cells are not getting the sugar they need for normal energy. And, second, the blood sugar raises to dangerous levels in the blood, causing tissues to become saturated with sugars, which causes these tissues to lose their flexibility and, eventually, their function. This is why diabetes are at a much higher risk for conditions like heart disease, and why they suffer nerve and blood vessel damage.
Diabetes is diagnosed by testing the amount of glucose in the blood. Ideal blood sugar never goes above 100 mg/dL. A fasting blood sugar of 126 mg/dL or higher, or any reading 200 mg/dL or higher on two occasions constitutes diabetes. A person with higher than normal readings, but below diabetic levels is sometimes said to be pre-diabetic, or insulin resistant. However, if your blood sugar is in the normal range, that may not tell the entire story. If you are insulin resistant but can produce extra insulin to keep your blood sugar in the normal range, that will not show up in a blood test that measures only your glucose.
So why would cells become resistant to insulin? There are many factors that go into this process, including simple aging. While not all of the factors are understood or, likely, even known, I plan to discuss many of them here. But at the simplest level, it might help to look at it like this: Cells require energy. When insulin is detected, the cells sends its glucose transporters to the surface of the cell and extracts glucose from the blood.
Now imagine a person who is inactive and eats a large amount of glucose-producing refined carbohydrate foods (as so many in the US do). Now the cells energy requirements are very low, but they are continually bombarded by ever increasing signals from insulin to come get more glucose. After a while, a cell may become less responsive to these signals. The number of insulin receptors in the cell may decrease. After all, why waste effort building insulin receptors when the cells gets more insulin signals and glucose than it knows what to do with.
Obviously, it gets much more complex than this. There are many hormones in play here, which all interact with each other. But this seems to be at the core, and eating less carbohydrates, especially refined carbohydrates, and increasing exercises seems to be the best way to prevent diabetes, and the best way to minimize diabetes once it occurs.
Insulin resistance is the condition where the body’s response to insulin is significantly diminished. Lifestyle and genetics can push insulin resistance to the point where it becomes a serious problem. Pushed to the extreme, glucose levels will continue to rise as the pancreas falls further and further behind, and the result is type II diabetes. In fact, some degree of insulin resistance is expected and normal as we age. Unfortunately, way too many people today are making lifestyle choices that are making insulin resistance a global epidemic.
As mentioned, type II diabetes is initially a disease of insulin resistance rather than problems producing insulin. Indeed, type II diabetics generally produce more insulin than the average person until it gets burned out or damaged from the disease. If you are at risk for diabetes but your blood tests show a normal glucose level, those tests may not be telling the whole story. It’s possible for a person to be producing high quantities of insulin, resulting in a normal glucose reading. Such a person may not know they are at risk of developing diabetes, and high levels of insulin–a condition called hyperinsulinism. Hyperinsulinism can cause a number of adverse health effects on its own, which may include hypertension (high blood pressure).
People with insulin resistance are likely to have a number of other conditions, which tend to occur together. These conditions, together, are called metabolic syndrome (formerly known as syndrome X). These conditions include excessive abdominal fat, blood fat disorders (including high triglycerides, low HDL (good) cholesterol, high LDL (bad) cholesterol, high blood pressure, whole-body inflammation, and other conditions). These conditions are reaching epidemic proportions in the US largely as a result of poor lifestyle.
In general, modern populations tend to get too many calories, eat foods that are too refined, and exercise too little. Refined carbohydrate foods can quickly be converted to blood sugar. Eaten in large quantities, this diet can flood the system with blood sugars. And with people who are inactive, their cells need very little sugar for energy. It’s little wonder that cells can stop “listening” to insulins signal to extract more sugar from the blood.
A diet that involves less overall calories, less fats (particularly saturated fats), less refined carbohydrates (sweets!), and more whole foods and fiber, and regular exercise have been shown to reduce the risk of the metabolic syndrome and diabetes.