Insulin, a hormone made by the pancreas, allows cells to absorb glucose so that it can be used as energy. The cells of individuals with insulin resistance are unable to use insulin effectively.
When cells cannot absorb glucose, it builds up in the blood. If glucose levels are higher than normal, but not high enough to be diagnostic for diabetes, it is referred to as prediabetes.
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 explain the signs and how it can be avoided.
Contents of this article:
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 itself does not present any symptoms if it occurs without prediabetes or diabetes
- Blood sugar levels with insulin resistance are normal
- Insulin resistance alone is not treated, but preventing prediabetes or diabetes from developing can be achieved through lifestyle measures
What is insulin resistance?
Insulin resistance shares similar risk factors to cardiovascular disease.
Around 15-30 percent of people with prediabetes go on to be diagnosed with type 2 diabetes within 5 years, according to figures from the Centers for Disease Control and Prevention (CDC).
Similarly, the American Heart Association (AHA) say that about half of people with high blood sugar go on to develop type 2 diabetes within a decade.
The AHA also point out that this means half of these people do not develop diabetes - "your choices make a difference."
In other words, individuals can reduce their chances of progressing to type 2 diabetes in the future by making some preventive lifestyle changes. Not only that, but these steps can also reduce the risk of a range of other potential problems including cardiovascular disease.
Signs of insulin resistance
If diabetes has not developed, insulin resistance does not normally present any symptoms.
Acanthosis nigricans - sometimes, a condition called acanthosis nigricans can develop in individuals with insulin resistance. The condition is marked by dark patches developing on the groin, armpits, and back of neck.
Polycystic ovarian disease (PCOS) - this is an endocrine disease. High levels of insulin can worsen the symptoms of PCOS.
During prediabetes, the pancreas works overtime to release enough insulin to overcome the body's resistance and keep blood sugar levels down. Over time, the pancreas' ability to release insulin begins to decrease, which leads to the development of type 2 diabetes.
Unless prediabetes and diabetes develop, insulin resistance presents no symptoms.
When prediabetes develops, insulin resistance is assumed to have contributed to the raised blood sugar and remains part of the problem.
In fact, insulin resistance remains a major part of type 2 diabetes alongside reduced insulin secretion from the pancreas.
Symptoms of diabetes include:
- Increased thirst and/or hunger
- Increased need to urinate
- Blurry vision
- Having cuts or sores that do not heal
How does insulin resistance develop?
The question of how and why insulin resistance develops remains complex and not fully understood.
The following outlines our current understanding of the process:
- The cells of the body develop a resistance to the effects of insulin.
- 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 (which stores glucose), to hold on to its glucose and store it rather than release it into the blood. Glucose is packaged up for storage in the liver in the form of glycogen.
- Insulin normally maintains a fine energy balance, never allowing the blood glucose level to rise too much for too long.
- Resistance initially results in the pancreas simply secreting more insulin to maintain safe blood glucose levels and keep high blood sugars at bay.
- Insulin resistance can eventually be accompanied by persistently higher glucose levels (prediabetes), and then the persistent hyperglycemia of type 2 diabetes; the release of extra insulin cannot be maintained to compensate for the increasing insulin resistance.
Some of the risk factors for prediabetes and diabetes are also risk factors for heart disease and other cardiovascular and cerebrovascular problems such as stroke.
Because some of the risk factors are also avoidable - and because obesity, in particular, has become more widespread - there has been an increased focus on lifestyle measures that can help reduce the chances of disease.
The following are all risk factors for insulin resistance, prediabetes, and diabetes, and some can be modified by lifestyle changes or medical help:
- Overweight and obesity (primarily abdominal obesity)
- Sedentary lifestyle - not engaging in physical activity regularly
- Sleep issues
The United States Department of Health and Human Services recommend that all people who are overweight and over 45 years of age should be tested for diabetes.
Diagnosing insulin resistance
A number of tests can be used to diagnose prediabetes and diabetes:
- A1C test - measures average blood sugar over the previous 2-3 months
- Fasting blood glucose test - glucose levels are checked after not eating or drinking for 8 hours
- Random blood draws - blood glucose levels checked at any time of the day
Preventing insulin resistance
While the risk factors for insulin resistance and type 2 diabetes are not always modifiable - our family history and genetic makeup, for example - there are proven ways to reduce the chances of becoming insulin resistant and developing type 2 diabetes. Obesity is a particular risk factor.
Some of the same factors are also important in preventing heart disease and stroke.
For ideas about diabetes prevention, the AHA simply say: "Lose weight and get active."
Prediabetes is only a warning. Landmark studies such as the Diabetes Prevention Program show that lifestyle changes can reduce the risk of progressing from prediabetes to diabetes by over 58 percent.