Insulin resistance, its causes and prevention
Insulin is a hormone, which is produced by the beta cells of the pancreas. The beta cells are scattered throughout the pancreas in the form of small clusters, called the islets of Langerhans. Insulin is an essential hormone that performs many actions in the body. Insulin regulates how the body uses and stores glucose and fat. Insulin controls blood glucose levels by signaling the liver, muscle and fat cells to take in glucose from the blood. It, therefore, helps cells to take in glucose to be used for energy. If the body has sufficient energy, insulin signals the liver to take up glucose and store it as glycogen. The liver can store up to around 5% of its mass as glycogen.
Insulin resistance is a condition, in which the body’s cells become resistant to the effects of insulin. As a result, higher levels of insulin are needed in order for insulin to have its proper effects. So, the pancreas compensates by trying to produce more and more of insulin until the pancreas can no longer produce sufficient insulin for the body's demands. This leads to increased glucose production by the liver causing the blood sugar to rise in the body. Insulin resistance has also been arbitrarily defined as the requirement of 200 or more units of insulin per day to attain glycemic control.
The prevalence rate of insulin resistance worldwide ranges from 2-16%. Insulin resistance is an important risk factor for development of diabetes.
Causes of insulin resistance –
Some of the important causes are enumerated below –
Genetics – In many cases of insulin resistance, there is an inherited component, which has a very strong influence on it. So far several different genes have been shown to carry abnormalities producing severe insulin resistance. And many others remain to be discovered. The strength of the effect of abnormalities in these genes is very variable.
Infection and illness – The development of acute insulin resistance has been reported following injury or critical illness. The experts hold the tissue specific mechanisms responsible for the development of acute insulin resistance. It is yet not clear whether those mechanisms differ following different injuries or critical illnesses.
Obesity – Fat cells are more insulin resistant than muscle cells and, therefore, obesity is an important cause of insulin resistance. As long as the pancreas is producing enough insulin, the body will overcome insulin resistance, but when the pancreas can no longer keep up producing high levels of insulin, blood sugar will start rising up, leading to type-2 diabetes.
Pregnancy – During pregnancy, a pronounced physiological decrease in peripheral insulin sensitivity occurs as pregnancy proceeds leading to increased insulin resistance. On the other hand, obese women, an increasing part of the fertile female population, develop a more pronounced insulin resistance during pregnancy with a higher risk of developing gestational diabetes mellitus, which is a pathological state of carbohydrate intolerance beginning or first recognized during pregnancy. And it leads to increased risk of adverse pregnancy outcome.
High blood pressure – The modern lifestyle, characterized by energy and sodium rich diet, sedentary life and high stress, favors positive energy balance. In the long term, positive energy balance creates the need for surplus fat storage. Ultimately, it leads to obesity, increasing the risk for chronic systemic low grade inflammation and subsequent insulin resistance and hypertension. Therefore, inflammation is a link between high blood pressure and insulin resistance.
High triglycerides – Triglycerides are chemical compounds digested by the body to provide it with the energy for metabolism. Triglycerides are the most common form of fat in the body and the most common that we digest. Altered lipid metabolism might contribute to the development of insulin resistance. A key tissue for the development of insulin resistance is muscle. Studies demonstrate that increased muscle triglyceride content can lead to the development of insulin resistance. There is growing evidence that excess muscle and liver lipid accumulation causes or exacerbates insulin resistance as in type-2 diabetes.
Stress – Stress increases body’s demand for energy whether it is acute or chronic stress. As a result, due to the release of hormones adrenaline or cortisol, blood glucose level is increased in order to meet increased demand for energy by the body. In a crisis situation, most of the cells resist insulin, so that the muscles involved in fighting or fleeing will have more energy. Acute stress may be over after a variable period of time but modern stresses often act on us 24/7, week after week. Over time, insulin resistance builds up leading to its attendant complications.
Physical activity – Chronic physical inactivity and obesity underlie the development of insulin resistance. Regardless of age, athletes are more insulin sensitive than normal-weight sedentary subjects, who in turn are more insulin sensitive than obese subjects. Studies demonstrate that insulin resistance may not be associated with aging per se but rather with lifestyle patterns linked with aging, such as a reduced physical activity and obesity.
Preventing insulin resistance –
The following measures will largely prevent the onset of insulin resistance –
- Healthy diet – Eat a diet high in vegetables and fruits of an array of colors that offer best of nutrients.
- Avoid bad carbohydrates – Choose whole grain foods. Healthy grains include barley, oats and brown rice. These foods are rated low on the glycemic index, which measures the effect of carbohydrates on blood glucose levels in the body.
- Choose snacks carefully – Take snacks such as nuts, beans and dry fruits which have low glycemic index. Avoid salty and processed snacks like chips or pretzels.
- Exercise regularly - Aim for moderate physical activity such as walking or jogging for at least 2 1/2 hours a week. Incorporate resistance training or weight training, into your routine at least twice a week. You may start out slowly, even exercising in 10-minute increments.
- Keep a healthy body weight – Maintain a healthy body weight as per your height and age. If over weight or obese, losing as little as 10 lbs of weight can help prevent insulin resistance.
- Check blood pressure regularly - Blood pressure levels above 130/85 may put you at risk for insulin resistance. If you have high blood pressure, consult your doctor for exercise and diet solutions to lower the numbers. Your doctor may also prescribe medication to regulate your blood pressure, thus lowering your risk of insulin resistance.
- Monitor blood cholesterol levels – Know your blood cholesterol numbers. Diet, exercise and cholesterol lowering medications can all help lower your numbers to a range that can help prevent insulin resistance or type-2 diabetes.
According to reliable estimates, as many as 1 in 3 individuals will develop diabetes by 2050, if the present trends continue. Insulin resistance can be tolerated by increased production of insulin from the pancreas, while putting the pancreatic beta cells under considerable strain in the process. Aside from predisposing to type-2 diabetes, insulin resistance alone is associated with early cardiovascular mortality, renal dysfunction, deterioration of the retina, and neuropathy. So, in view of these potential complications of insulin resistance, it is of paramount importance to prevent its onset.