Insulin is an essential hormone for life. Produced by cells in the pancreas, it is released after a meal in response to increased blood sugar levels. Insulin has receptors on many cells in the body: liver, muscles, brain, adipose tissue, etc. When the glucose level increases in the blood, it informs the cells that they must “open their doors” to the glucose and therefore has a hypoglycemic effect.
In type 1 diabetes, the immune system attacks insulin-producing cells, forcing patients to have regular injections of the hormone. But the situation is different in type 2 diabetes, where the problem with blood sugar control does not come from a lack of insulin. Insulin resistance is a cause of type 2 diabetes.
What is insulin resistance?
“In its simplest form, insulin resistance is a reduced response to insulin”explains Dr. Bikman.
The notion of insulin resistance dates back to the work of Himsworth (1) who noticed in the 1930s that the injection of glucose and insulin into diabetic patients produces two results: some, described as insulin sensitive , respond with stable or decreased blood sugar levels, while others see their blood sugar levels increase. The latter are resistant to insulin: at a normal plasma insulin level, the target tissues are unable to mount a normal response to reduce blood glucose levels. This insulin resistance requires increased hormone secretion to compensate, such that fasting plasma insulin levels increase and glucose levels remain elevated due to insulin ineffectiveness.
Result : “Type 2 diabetes is insulin resistance that has progressed to the point where the body is unable to maintain blood glucose levels below the clinically relevant threshold of 126 mg/dL.”says Dr. Bikman.
There are different possible causes of insulin resistance. Insulin resistance is found in people suffering from obesity and metabolic syndrome (2). Oxidative stress, inflammation but also the intestinal microbiota are probably key players in the progression of insulin resistance (3). Fructose consumption is a contributing factor (4).
How to know your risk of insulin resistance
In his book Insulin resistanceBenjamin Bikman offers a questionnaire to briefly assess your risk. But for more precise information, you need to know your fasting insulin level, using a blood test. “This dosage is often covered by health insurance and/or your mutual insurance company, but not always (and this is why the doctor may be reluctant)he explains. If you don’t want to wait for a medical appointment, you can simply request a dosage on your own. »
But what insulin level is worrying? “Ideally, your blood insulin level should be less than ≈6 microunits per milliliter of blood (μU/mL). » He also advises have your blood sugar measured at the same time, as this will help calculate the HOMA index. Ask your medical analysis laboratory to find out the cost of an analysis if you do not have a prescription.
Read: HOMA test: insulin resistance is important to know if you are healthy
A common condition
In the United States, one in three people are considered prediabetic (5). As Benjamin Bikman points out in his book, insulin resistance was once a disease of affluence or a pathology that mainly affected wealthy elderly people, but that has changed: “There are documented reports of children as young as 4 years old being insulin resistant (and up to 10% of North American children are affected). Additionally, the total number of people with the disease in low-income countries is now higher than in high-income countries.. To top it all off, the overwhelming majority of people who suffer from insulin resistance don’t know they have it and have never heard of it! »
The prevalence of insulin resistance varies between countries. Among European adults, it would be around 15.5%, while higher rates have been reported elsewhere in the world, reaching 23% in Thailand, 39% in Texas, 44% in Lebanon and 46% in Venezuela (6).
Insulin resistance and chronic pathologies
Insulin resistance is not just the condition that precedes type 2 diabetes, warns Dr. Bikman. “Insulin resistance plays a role in a surprising number of very serious chronic diseases, including problems with the brain, heart, blood vessels, reproductive organs, and more. Much more than a simple inconvenience, it is a serious illness when left untreated. Most people who experience insulin resistance will eventually die from heart disease or other cardiovascular complications. Others will develop Alzheimer’s disease, breast or prostate cancers, or other life-threatening illnesses. »
Thus different studies show that:
- insulin resistance is a cardiovascular risk factor in diabetic and non-diabetic people (7);
- insulin resistance and inflammation have been implicated in fatty liver disease or NAFLD (8);
- Insulin resistance is common in women affected by polycystic ovary syndrome or SOPK (9);
- according to a cohort study carried out in the Netherlands, people with insulin resistance are twice as likely to develop an major depressive episode (10).
What to do to avoid insulin resistance
To limit insulin resistance, you must act on the main contributing factors and in particular improve your diet to lose weight, for example with a low-carbohydrate diet and/or intermittent fasting. Other steps to take include:
- engage in regular physical exercise (11);
- stop smoking (12);
- improve your sleep (13);
- reduce stress (14)…
