What Is Insulin Resistance?

Our bodies rely on the energy we get from food. The hormone insulin, which the pancreas produces, plays a key role in this process. It acts as a signal that tells our cells to absorb sugars and convert them into the energy we need to live.

For those with insulin resistance, however, things work differently. Their body cells don’t respond to the signal insulin sends as readily, so it takes higher levels of insulin to convert sugar into energy. The pancreas tries to overcome this resistance by increasing insulin production to regulate the blood sugar.

In people who are predisposed, for example through genetic risk, the pancreas can’t make enough insulin to keep up with demand. This causes blood sugar levels to increase to unhealthy levels, and can lead to conditions such as diabetes.

Deborah J. Wexler, MD, MSc, is a Mass General Brigham endocrinologist. She is the associate clinical chief of the Massachusetts General Hospital Diabetes Unit, and clinical director of the Mass General Diabetes Center. Dr. Wexler answers common questions about insulin resistance, including its causes and how it is treated.

What is the main cause of insulin resistance?

There are many potential causes for insulin resistance, but it often develops in people who carry extra weight.

“Extra weight ends up getting stored in places it shouldn’t be, like the liver and other tissues,” Dr. Wexler explains. “Some people tend to gain weight in their upper bodies while other people tend to store their excess weight in their hips or lower bodies. It’s the ‘apple shaped’ people who tend to have more problems with insulin resistance, because the excess weight is being stored in the liver and other abdominal organs.”

You do not have to be obese or overweight to develop insulin resistance. Risk factors for insulin resistance can also relate to a person’s lifestyle or genetics. For example:

• Age: Adults 45 and older are at a greater risk for insulin resistance than younger adults.
• Ethnicity: Those with Asian, Latinx, African, and Native American heritage are at a greater risk of developing insulin resistance and diabetes.
• Family history: Sometimes insulin resistance runs in families.
• Certain medications: These can include some antidepressants, steroids, some blood pressure medications, and birth control pills, among others.
• A sedentary lifestyle: Sitting too long for too many hours a day can lead to problems. Break up your day with physical activity such as walking, biking, or even mowing the lawn. 
• Trouble with sleep. Work, stress, sleep disorders, restless leg syndrome, and other factors can cut back on the rest you need to stay healthy.
• Genetic syndromes, such as lipodystrophies and other syndromes, may cause insulin resistance. Lipodystrophies are conditions where the body uses or stores fat in an abnormal way. 

What other conditions do people with insulin resistance typically have?

Many conditions can coexist with insulin resistance. According to Dr. Wexler, these include:

• Fatty liver. “The liver is the factory that processes our energy,” says Dr. Wexler. “When we overeat, the fat goes straight to the liver. That extra fat sitting in the liver then interferes with the body’s ability to respond appropriately to insulin.”
• Polycystic ovarian syndrome (PCOS). “PCOS is characterized by irregular menstrual cycles. People with PCOS often have insulin resistance with high insulin levels,” says Dr. Wexler.
• Type 2 diabetes. “People often say that insulin resistance causes type 2 diabetes,” Dr. Wexler says. “That’s not always true. There are many people who have insulin resistance and are overweight with fatty liver but don’t have type 2 diabetes because their pancreas just produces more and more insulin and keeps up with the body’s demand. Type 2 diabetes develops when insulin production declines.”

What is the treatment for insulin resistance?

“The best treatments for insulin resistance are the best treatments for overweight or obesity. They’re also the best ways to just stay healthy overall,” says Dr. Wexler. They include:

• Losing weight if you are above your target weight: Your doctor can help you figure out a healthy weight goal for you. They also may be able to recommend support people, like nutritionists, who can guide you on your weight loss journey.
• Healthy eating habits: “Relatively simple steps like eliminating sugary beverages and having portion-controlled, balanced meals can be very beneficial for insulin resistance,” says Dr. Wexler.
• Exercise: “Exercising reduces insulin resistance even when you aren’t losing weight,” says Dr. Wexler. “Simple steps, like walking 30 minutes over the course of the day or taking the stairs, really make a difference over time.”

“Insulin resistance isn’t a disease in and of itself; it’s a phenomenon that goes along with many other conditions,” says Dr. Wexler. “Simple steps can improve insulin resistance and reduce the risk of a lot of the health conditions that go along with it.”