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- Insulin resistance is when cells are less responsive to insulin and can't as easily absorb sugar.
- Insulin resistance symptoms are rare, therefore, your doctor will diagnose you with glucose tests.
- Insulin resistance can be managed and even reversed through proper diet and exercise.
- Visit Insider's Health Reference library for more advice.
Insulin resistance, also known as impaired insulin sensitivity, is when someone has built a tolerance to insulin, the hormone responsible for regulating blood sugar levels.
Although insulin resistance precludes the development of type 2 diabetes, not everyone who has the condition will develop type 2 diabetes or its precursor, prediabetes. In fact, insulin resistance can be reversed with proper diet and exercise.
Here is what causes insulin resistance, how to recognize it, and the best treatment options.
What is insulin resistance?
Insulin resistance occurs when the cells in your muscles, fat, and liver are less responsive to insulin and therefore struggle to absorb glucose – aka sugar – in the blood.
Typically, you get a boost of sugar in your blood after you eat something containing carbohydrates. This boost signals to your pancreas to release insulin, which then helps your cells absorb the sugar and convert it to energy so you can function normally. Insulin resistance disrupts that process.
"When cells in the body become insulin resistant, more insulin is required to do the same job [aka lower blood sugar levels]," says Daniel Vatner, MD, an endocrinologist at Yale School of Medicine. "A person with insulin resistance needs to make much more insulin after a meal, or they will not be able to store and use sugar properly."
However, your body can only produce so much insulin on its own. So, there's a critical tipping point where your cells become so insulin resistant that they lose control over your blood sugar, and you end up with dangerous, chronically high blood sugar levels.
When there's too much sugar in your blood for too long, your body eventually stores it as fat. That's why insulin resistance increases the risk of being overweight and obesity-related conditions like:
- Elevated blood pressure
- High triglyceride levels - a type of fat that contributes to the hardening of arteries
- Stroke
- Polycystic ovary syndrome (PCOS)
Symptoms of insulin resistance
Insulin resistance rarely comes with any noticeable symptoms. And most tests designed to detect insulin resistance are complicated and expensive.
Therefore, a healthcare provider will usually rely on tests that assess your blood sugar levels. These tests include:
- A1C test, which measures your average blood glucose levels over the past two to three months.
- Fasting glucose test, which tests blood sugar levels after not eating or drinking for at least eight hours.
- Glucose tolerance test, which measures blood sugar levels both before and after consuming a sweetened beverage. However, this is used less frequently since it's not as simple or affordable to administer.
All of these tests can also be used to diagnose prediabetes.
In rare cases, some people with insulin resistance may also develop a skin condition called acanthosis nigricans. This condition causes the skin to develop thick, dark, purplish patches, typically in the underarms, groin, or on the back of the neck.
What causes insulin resistance?
Being overweight or obese can significantly increase your risk of insulin resistance, says Vatner.
"As an individual gains weight, fat can accumulate where it doesn't belong, as in the liver or the muscle," he says.
As fat gets into the cells, it can interfere with the cells' ability to respond to insulin, forcing the pancreas to make more insulin to compensate.
However, people of any size can also become insulin resistant.
You should regularly monitor blood sugar if you have risk factors for insulin resistance, such as obesity, a sedentary lifestyle, or a family history of type 2 diabetes. Even if you don't have these risk factors, you should start getting tested at the age of 45, says Mark Schutta, MD, medical director of the Penn Rodebaugh Diabetes Center.
How to treat insulin resistance through diet
Exercising and eating healthy are the most effective strategies for reversing insulin resistance. Even just a 5% to 10% loss in body weight can help to reverse insulin resistance, says Vatner.
Exercise not only plays an important role in weight management but can also help people with insulin resistance manage blood sugar. A 2016 review found that regular, moderately-intense physical activity - like walking or biking - for at least 30 minutes, three to five days a week was associated with improved insulin sensitivity as well as blood sugar control.
Schutta advises starting with a brisk 30- to 45-minute walk several days a week and then working your way up to 150 minutes of weekly moderate to vigorous aerobic exercise.
Diet also plays a crucial role in managing and reversing insulin resistance. If you have insulin resistance, physicians may suggest you follow the Mediterranean diet, a plant-based diet, or a low-carb diet, like the Atkins diet.
In general, Schutta recommends limiting your intake of:
- Refined carbohydrates such as white bread, pasta, and rice
- High-glycemic fruits such as watermelon, pineapple, grapes
- Starchy vegetables such as corn, squash, and potatoes
- Saturated fat, which is in foods like full-fat dairy, butter, lamb, and pork
Schutta also recommends eating more:
- Lean protein, such as skinless chicken and turkey, shrimp, low-fat Greek yogurt
- Monounsaturated fats such as nuts and seeds, olives, and avocados
- Low-glycemic fruits such as berries, apples, pears
- Non-starchy vegetables like asparagus, carrots, and tomatoes
- Beans and legumes such as chickpeas, lentils, black beans
Vatner says insulin-resistant patients with co-occurring conditions may be prescribed the following medications:
- Metformin to treat high blood sugar levels, particularly for women with PCOS
- Pioglitazone to treat high blood sugar levels, particularly for people with fatty liver disease
- Weight-loss medications, especially GLP-1s like Semaglutide and Liraglutide, for those very overweight
Insider's takeaway
Insulin resistance is a serious, but treatable condition. If left untreated it could develop into prediabetes, metabolic syndrome, or type 2 diabetes, all of which increase your risk of heart disease and stroke.
While insulin resistance does not have any symptoms, it can be diagnosed through a blood sugar test.
To treat and reverse insulin resistance, eat a healthy diet full of fruits, vegetables, lean proteins, and whole grains while exercising for at least 150 minutes a week.