How to Measure Insulin Resistance
Going beyond BMI and A1C.
If you ask the average person on the street to play a word association game with diabetes, the word “fat” will come up sooner rather than later. Links between obesity and Type 2 diabetes are well established. And yet, not all fat people have diabetes, and not all people with diabetes are fat. Like many things connected to diabetes, simple and ubiquitous explanations almost never work.
According to the U.S. Center for Disease Control, 100 million Americans are now obese, with a Body Mass Index (BMI) of 30 or higher. At the same time, the CDC reports that as many as 80 million Americans were insulin-resistant, and since insulin resistance is a precursor to diabetes onset, the two numbers seem to support one another.
The correlation breaks down, however, if one assumes that obesity and insulin resistance are always connected. They aren’t; some 12% of those who are insulin-resistant are thin. Since testing only overweight people isn’t a diagnostic solution, heading off diabetes Armageddon in the future boils down to identifying insulin-resistant people, regardless of weight, say diabetes researchers. Early identification of insulin resistance can have a major impact on the long-term prognosis of diabetes in patients, or help patients avoid the onset of diabetes altogether, but the window for early diagnosis of insulin resistance often is missed. Standard tests such as A1c percentages or fasting glucose won’t always identify the problem in time to allow prevention to work.
How Insulin Resistance Begins
Insulin resistance is a metabolic condition that causes the body’s cells to require a higher than normal amount of insulin to convert glucose into energy. Besides having a predisposition to diabetes, insulin-resistant people may have other health issues, too, including high blood pressure, high cholesterol, heart disease, and polycystic ovarian syndrome (PCOS), a leading cause of infertility issues.
“When a person becomes resistant, they need much more insulin to do the same work,” explains Dr. Yehuda Handelsman, the president of the American Association of Clinical Endocrinologists and a Los Angeles-based endocrinologist. “What happens is that when the body recognizes there is resistance, the pancreas responds with higher insulin levels. As long as the pancreas can respond with higher and higher insulin levels, a person will not have diabetes.”
Handelsman goes on to explain that up to 40 percent of people with insulin resistance also have a defect in their insulin-producing beta cells that prevents the pancreas from producing insulin beyond a certain level of demand. This “insulin max” is different for every affected individual, but ultimately an individual pancreas reaches its maximum insulin output and then starts to “burn out.” Over time, those affected will need medications, including injected or infused insulin, to cope with the problem of excess glucose in the bloodstream.
Insulin resistance researchers have learned that an increased amount of fatty acids and inflammation from obesity causes cells to require more insulin to do the same job. Losing weight and increasing activity can mitigate this, but the genetic predisposition to insulin resistance is beyond a person’s control.
Before we begin to dwell on obesity as a principal cause of resistance, metabolism throws us a curve in that some insulin-resistant people are thin. Doctors theorize that the genetic beta cell defect predisposition is much higher in this group.
In addition, some thin people are what is colloquially called “skinny fat,” meaning that although they may look thin on the outside, their body actually has a high percentage of body fat compared to muscle. The fat can be “hidden” in areas like muscle tissue and deep in the abdomen. This fat is called visceral fat, which is harder to see and more damaging than fat directly under the skin. A high body fat ratio leads to insulin resistance, even if a BMI scale puts them below 30, the number at which obesity begins.
Tools To Detect Insulin Resistance
Pre-diabetes can exist for a long time in your body without triggering the most common outward signs of diabetes (continual thirst, frequent urination, blurred vision, etc). And standard methods of detecting insulin resistance or pre-diabetes using glucose tolerance tests or an A1C percentage often show false negatives; that’s because the pancreas is still able to produce enough insulin to overcome insulin resistance. Type 2 diabetes is also good at hiding itself; it is common that someone diagnosed as a Type 2 has already had the disease for five years, which makes the battle for control an uphill climb even before it begins.
Fortunately, there are other ways to identify insulin resistance using biomarkers in blood drawn from patients as a normal part of an annual or semi-annual general checkup. These biomarker data can be plotted against what is considered normal, and as a result, place the person at a specific point along the path to pre-diabetes or to Type 2 diabetes itself.
Tools to detect insulin resistance include
- Tests showing the degree of pancreatic output and what could be defined as “pancreatic stress”. These include both fasting insulin and fasting glucose, a Homeostasis Model Assessment (HOMA) that measures beta cell function and insulin sensitivity, a C-Peptide test and a pro-insulin test;
- Measurements of lipid hormones such as leptin and adiponectin. These biomarkers can give insight into a person’s unique communication between fat metabolism and insulin.
- Tests that evaluate a person’s degree of inflammation.These biomarkers include a cardiac-specific C-reactive protein measurement (CRP) and a sedimentation rate.
Measurements that quantify fatty acid metabolism and the fatty acids released by the patient. These can also give particle size and number as well as an average inflammatory number.
Companies offering these kinds of screening tests include Genova Diagnostics (www.gdx.net) and Metabolon (www.Metabolon.com). Dr. Margarita Ochoa-Maya, an endocrinologist and CDE in Manchester, New Hampshire, says that she often uses the Genova “preDguide” and “metSynguide” tests to identify those at risk.
“The ideal candidate for this in-depth testing is a person in which there is strong family history of diabetes, who may not be fat, yet presents other features that point in the direction of metabolic imbalance, such as elevated cholesterol or hypertension,” says Dr. Ochoa-Maya. “It is also a great resource for patient education and motivation in order to start their lifestyle change sooner rather than later.”
Metabolon exhibited its new insulin-resistance test, Quantose, at this year’s American Diabetes Association’s Scientific Sessions in Chicago. Quantose is a blood test for certain biochemical markers that are associated with insulin resistance, which can inform a patient of their level of risk for Type 2 diabetes.
“It’s tremendous because that’s the point in time that a person could reverse the onset of diabetes by all kinds of intervention, diet and exercise and metformin,” explains Kathryn Lawrence, Director of Marketing for Metabolon.
A patient interested in such a test can talk with their doctor. Before asking for a test, however, it pays to call your insurance provider to see what’s covered, as the tests are expensive, says Dr. Ochoa-Maya. Lawrence says that many patients, including Medicare patients, have been able to get insurance coverage for the tests.
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