The sensitivity of the body to insulin (insulin sensitivity)
In the human body, glucose (glucose) is the primary source of energy. This means that the cells of the body prefer glucose as an energy source. Glucose is found in food and drink (in the form of carbohydrates) and the liver can also produce new glucose between meals. In order for the body’s cells to absorb glucose, insulin is required. It is in the pancreas’s so-called beta cells that insulin is made and this happens when we eat or drink. Then the pancreas knows that glucose will soon enter the bloodstream and insulin is needed to enable the cells to take up the glucose.
It is mainly the liver, fat and muscle that need insulin to take up glucose. In fat, glucose is absorbed and converted into ordinary fat (that’s why you gain weight from eating too many carbohydrates). In muscles and in the liver, glucose is stored in the form of glycogen. For the body to function normally, it is important that the liver, fat and muscles can react normally to insulin. The term insulin sensitivity is used to describe how good/bad insulin affects liver, fat and muscle. If insulin sensitivity is high, then this means that insulin has a good effect. If insulin sensitivity is low, then insulin has a bad effect. Low insulin sensitivity means that the body’s cells do not react to insulin and therefore do not take sugar from the blood. Then the blood sugar rises and this is one of the main causes of type 2 diabetes. However, insulin resistance can actually also occur in type 1 diabetes.
If you have insulin resistance, it means that the body simply reacts too poorly to insulin. Then the blood sugar rises (because the cells do not take up the glucose) and the pancreas tries to compensate for this by making even more insulin. This condition, when you have abnormally high levels of insulin in the blood, is called hyperinsulinemia.
Situations and conditions that require more insulin
We know today that there are conditions and diseases that cause the body to require more insulin. Several of these conditions can affect people without diabetes.
- Stress — being stressed makes the effect of insulin worse.
- Infection with fever
- Overweight — This is one of the main causes of insulin resistance and the development of type 2 diabetes
- Chewing tobacco
- Low physical activity
Situations and conditions requiring less insulin
- After exercise.
- At weight loss.
- The first weeks after suffering from type 1 diabetes.
About insulin sensitivity
Type 2 diabetes
Approximately 80 -90% of people with type 2 diabetes have reduced insulin sensitivity and these individuals tend to have reduced insulin sensitivity several years before they are diagnosed. Insulin resistance and impaired glucose tolerance (IGT) are both precedes of type 2 diabetes and they actually pose an increased risk of cardiovascular disease. Insulin sensitivity leads to a vicious spiral. When the sugar in the blood is not absorbed by the cells due to impaired insulin sensitivity, the blood sugar rises, which leads to the pancreas trying to compensate by increasing release, which in turn leads to even worse insulin sensitivity.
Type 1 diabetes
Insulin is released by the pancreas, the blood of which goes on to the liver. Normally, insulin is first in the liver, but this is not the case if you have type 1 diabetes. People with type 1 diabetes have to inject insulin into the subcutaneous fat, and the blood that takes up the insulin does not go to the liver first. This causes insulin concentration in the liver to be lower for children with type 1 diabetes and there are theories that this explains why they generally grow slower and later enter puberty. However, it should be pointed out that children with type 1 diabetes actually reach their estimated body length in the end.
Consequences of impaired insulin sensitivity
- Elevated levels of insulin (hyperinsulinemia) — a condition that compensates for impaired insulin sensitivity by overproduction of pancreatic insulin. In the end, the pancreas becomes exhausted and can no longer produce insulin, which causes a sudden shortage of insulin. This explains why people with type 2 diabetes may need insulin after some time.
- Elevated blood sugar (hyperglycemia) — because the ability of cells to react to insulin is impaired, blood sugar rises. Elevated levels of blood sugar can even negatively affect the body’s insulin-producing (beta cells) cells.
- Elevated levels of blood lipids (hyperlipidemia) — reduced insulin sensitivity is associated with poor blood lipids. The healthy fat (HDL cholesterol) decreases while unhealthy blood lipids (triglycerides and LDL cholesterol) increase.
Characteristics of reduced insulin sensitivity
Individuals with reduced insulin sensitivity are often overweight, mainly they have abdominal obesity. Often they have high blood pressure and high blood lipids. Sometimes a particular type of skin change is seen in medical language called acanthosis nigricans (dark areas around skin folds).
Doctors treating patients with insulin resistance should regularly check the following tests:
- Fasting blood sugar (FP-glucose)
- Long-term blood sugar (HbA1c)
- Blood lipids (including apolipoproteins)
- Kidney function (microalbuminuria or macroalbuminuria)
- Blood pressure
- Body mass index (BMI)
- Waist circumference
- Symptoms of cardiovascular diseases.
Some clinics and medical receptions even examine non-fasting blood sugar a couple of hours after meals to determine the degree of insulin sensitivity. This is possible by studying the increase in blood sugar levels after eating. This is done in order to diagnose impaired sugar tolerance (IGT, impaired glucose tolerance) which often precedes reduced insulin sensitivity.
How to improve insulin sensitivity
Several factors affect insulin levels in the body, unhealthy lifestyle factors such as sugar-rich diet, fast carbohydrates, excess calories, stress and less exercise all lead to high levels of insulin in the body.
Fruit contains several important and healthy nutrients yet fruit also contains fructose which is a particular type of sugar and the more fructose you eat the more fat stores the liver. High-fat levels in the liver are associated with a condition called hepatic insulin resistance (reduced insulin sensitivity in the liver) which leads to reduced insulin sensitivity in other organs.
At stress, the body releases hormones called cortisol and adrenaline. These are two hormones that, among other things, contribute to elevated levels of blood sugar and also stimulate the body to excrete more insulin.
However, increased insulin release for a long period leads to impaired insulin sensitivity, increased secretion of insulin (hyperinsulinemia) is usually the root cause of type 2 diabetes, metabolic syndrome, overweight and obesity.
People with and without diabetes should strive for more sensitivity to insulin. Dietary rearrangement is probably the most important part to restore insulin sensitivity, but exercise and fasting variants also have proven positive effects. Studies show that resistance training leads to muscle growth and increased insulin sensitivity many hours after the workout.
- More sleep — lack of sleep leads to several unhealthy conditions and, above all, reduced insulin sensitivity. Less sleep than 4h per night increased the risk of reduced insulin sensitivity by 100%.
- Increased exercise — exercise is one of the best methods for increasing insulin sensitivity. Blood sugar is more easily absorbed by muscle cells. Insulin sensitivity is improved even in people without diabetes. A combination of resistance training and cardio training is probably the most optimal training plan.
- Reduced stress — poor sleep leads to increased secretion of the stress hormones cortisol and glucagon. These hormones lead to the breakdown of glycogen, which turns into sugar (glucose). Reduced sleep leads to reduced insulin sensitivity and activities such as merit, exercise and more sleep are all good methods to improve insulin sensitivity by reducing stress levels.
- Weight loss — abdominal obesity is a serious risk factor for type 2 diabetes and metabolic syndrome. A study at John Hopkins University in the United States observed that pre-diabetes people who lost 5-7 of their total body weight reduced the risk of type 2 diabetes by 54% over the next three years.
- More dietary fibres — more soluble fibres are associated with benefits that lower cholesterol levels and lower appetite. Fibers can contribute to better intestinal bacteria associated with better insulin sensitivity. Food such as porridge, flaxseed, vegetables (ex Brussels sprouts) and fruits (ex orange).
- More fruits and vegetables — all diets should include a lot of vegetables and good fruits.
- Various herbs and spices — some studies suggest that spices and herbs such as green tea, apple cider vinegar and cinnamon improve insulin sensitivity.
- Reduced carbohydrates, trans fats and sugars — carbohydrates are converted into sugar in the body and leads to increased levels of blood sugar thereof, low carbohydrate diet is important for insulin sensitivity. There is a big difference between added sugar and natural sugar. Natural sugar is found in plants and seedlings and contains many other nutrients. Several foods also contain fructose, which contributes to impaired insulin sensitivity.
Drug treatment for reduced insulin sensitivity
Metformin — studies have shown that the world’s most common antidiabetic medicine has a positive effect on insulin sensitivity and is likely to occur through reduced production of sugar (glucose) from the liver. Patients with impaired insulin sensitivity may be treated with Metformin and it is well suited for the treatment of obese people with type 2 diabetes.
Glitazones (Pioglitazion, Actos) — a group of medicines used to treat elevated blood sugar levels because it increases the absorption of blood sugar into the cell, which leads to better utilization of insulin in muscle and fat cells. In addition to reducing insulin resistance, the drug also has other beneficial effects on the cardiovascular system.
Diseases, risk factors and symptoms resulting from insulin resistance
Insulin sensitivity forms the core of the mechanisms of the disease behind overweight, obesity, type 2 diabetes and the metabolic syndrome. In addition, insulin resistance is associated with an increased risk of multiple types of cancer and cardiovascular diseases.
Insulin resistance leads to a specific type of lipid disorder that increases the risk of atherosclerosis of the heart and brain vessels (including other vessels), and this can lead to a heart attack and stroke.
It is important to know that reduced insulin sensitivity also contributes to high blood pressure (hypertension), high blood lipidemia (hyperlipidemia), skin diseases, polycystic ovarian disease (fluid-filled blisters on the ovaries), hemochromatosis (excessive accumulation of iron in the body), fatigue, increased hunger and difficulties in concentrating.
History of insulin sensitivity (insulin resistance)
The first description of reduced insulin sensitivity (insulin resistance) was in 1960 shortly after the development of a method that made it possible to quantify insulin levels in the blood (radioimmunoassays). Two researchers in the United States named Rosalyn Yalow and Solomon Berson defined insulin resistance as a condition “where a greater than normal amount of insulin is required to produce a quantitative normal response”.
In 1976, scientists proved that the insulin receptor was incorrectly formed in people exposed to elevated levels of insulin (hyperinsulinemia) for a longer period. Incorrect insulin receptors are strongly associated with impaired insulin sensitivity and also contribute to deterioration of insulin sensitivity.
How to calculate the degree of insulin sensitivity
Several methods have been developed to estimate the degree of insulin sensitivity in people with and without diabetes. The most accepted methods are called HOMA-IR and HOMA-B. HOMA-IR is an abbreviation for “Homeostatis model assessment-insulin resistance” and was first developed in 1985, HOMA-B is another mathematical formula that describes the degree of beta-cell dysfunction. In these equations, fasting sugar (glucose) and insulin were measured. You who have diabetes do not need to figure out your insulin sensitivity, but you can ask your doctor/nurse if you are interested in doing this.