An idea emerging from the fields of diabetology, cardiology and public health medicine, the science of insulin resistance has developed relatively recently.
It was not until the beginning of this millennium that insulin resistance and prediabetes began to receive heavy medical research focus.
There has been the terminology of insulin resistance syndrome, metabolic syndrome and even syndrome X, to denote the cluster of risk factors that is associated with insulin resistance.
By contrast, the classic urination and thirst of full diabetes have been understood since the 1600s, and the discoveries were made over a century ago for the roles of the pancreas and insulin in full diabetes.
Insulin resistance is now established as what lies behind the development of type 2 diabetes, but this is a bit more complex than it sounds. What is insulin resistance exactly, and why does it develop?
This page will look at the current understanding of insulin resistance and explain how it is a risk factor for both diabetes and other conditions. The article will also outline what can be done about it.
Fast facts on insulin resistance
Here are some key points about insulin resistance. More detail and supporting information is in the main article.
- Insulin resistance is a "silent" risk factor alongside other risk factors for diabetes and cardiovascular problems
- Insulin resistance remains a problem when it is no longer silent but behind the raised blood sugar levels of type 2 diabetes
- The phenomenon is complex and has only relatively recently become better understood in the science of diabetes
- Insulin resistance itself does not present any signs or symptoms when it appears alone without the development of prediabetes or diabetes
- Blood sugar levels with insulin resistance alone are also normal
- The process is instead assumed to be a risk factor for people who are also obese or overweight, have hypertension or a history of diabetes in the family, among others in a "cluster" of diabetes and cardiovascular risk factors
- Insulin resistance alone is not treated, but prevention of the 5-year and 10-year risks can be achieved through lifestyle and medical measures.
What is insulin resistance?
Diabetes shares some of the risk factors for cardiovascular disease.
Insulin resistance happens well before type 2 diabetes is diagnosed but it is still part of the full condition.1
It is a relatively new idea in medical science - insulin resistance is the phenomenon that is thought to raise the chances of developing prediabetes, the raised blood sugar level that can in turn eventually become high enough for type 2 diabetes to be diagnosed.2-5
There are estimates that around 15-30% of people with prediabetes go on to be diagnosed with full diabetes within 5 years, according to figures from the Centers for Disease Control and Prevention (CDC).6
The American Heart Association (AHA) highlights a longer outlook - the 10-year risk. They say that about half of people with high blood sugar go on to develop type 2 diabetes within a decade. But the AHA also point out that this means half of these people do not develop diabetes - "your choices make a difference."7
What the public health experts and specialist doctors mean by these statistics is that anyone with high blood sugar, insulin resistance, prediabetes, obesity or "metabolic syndrome" can reduce their future chances of developing full type 2 diabetes by taking some preventive steps.
These preventive steps, outlined on the next page, are a combination of lifestyle measures and medical help and monitoring that can reduce the established risks for diabetes. Not only that, but these steps can also reduce the risk of a range of other potential problems grouped under cardiovascular disease.
How does insulin resistance develop?
While there have been the developments of the past 10-15 years, the question of how and why insulin resistance develops (the pathogenesis of it) remains complex and not fully understood.1,4
What is established is that people with risk factors, including genetic and lifestyle factors:1,4
- Might develop a resistance to the effects of the hormone insulin, which is secreted from the pancreas
- Insulin is essential for the regulation of the glucose circulating in the blood - it induces glucose to be taken up by the cells
- Insulin is also the chemical messenger that signals to the liver to hold on to its glucose rather than release it into the blood (glucose is packaged up for liver storage in the form of glycogen)
- Insulin normally maintains a fine balance that is just right for the amount of energy we need at the right time, and so keeps a predictable blood sugar level at different times between eating and activity, never allowing the blood level to rise too much for too long
- However, resistance to the hormone can develop
- Resistance initially results in the pancreas simply secreting more insulin, however, to maintain safe blood glucose levels and keep symptoms at bay - this is the picture when insulin resistance is unaccompanied by additional illness
- However, insulin resistance can eventually be accompanied by the persistently higher glucose levels of prediabetes, and then the persistent hyperglycemia of full diabetes; the release of extra insulin cannot be maintained in compensation for the increasing insulin resistance.
There is great complexity in how insulin resistance develops, and especially for why it develops, but the good news is that there are plenty of ideas about how to prevent it. And when type 2 has not been prevented, it can be managed.
On the next page, we look at the signs of insulin resistance, associated risk factors and methods of prevention.