When you eat, food is broken down into sugar and released into the bloodstream. Insulin, a hormone made by the pancreas, signals cells to absorb that sugar and convert it into energy.
But sometimes this finely tuned system can get overwhelmed. When your cells don’t respond as well to insulin, glucose builds up in the blood. This is known as insulin resistance, and it increases the risk of prediabetes, Type 2 diabetes and other health concerns.
“Insulin resistance is often linked to obesity, but the truth is you don’t have to be overweight to develop it,” says Vishaal Gupta, MD, a Geisinger endocrinologist. “There are many causes of insulin resistance, from lifestyle habits to underlying health conditions — and it’s often not just one factor.”
The good news: Insulin resistance is common, and often reversible. Understanding what causes it is the first step toward protecting your long-term health.
What is insulin resistance?
Insulin is an essential hormone for regulating blood sugar. Think of it as a key, unlocking muscle, fat and liver cells so glucose (sugar) can enter and be converted into energy.
With insulin resistance, those cells don’t respond effectively to insulin’s signal. As a result, glucose has a harder time entering cells and begins to build up in the bloodstream. The pancreas then produces more insulin to try and keep blood sugar in check. This can work for a while, but as resistance (tolerance) increases, blood sugar rises and the pancreas works harder than it should.
Over time, prolonged insulin resistance and high blood sugar can lead to prediabetes or Type 2 diabetes.
“Insulin resistance isn’t a disease on its own, but it’s a condition that can cause a range of many other health problems,” says Dr. Gupta. “Unfortunately, it can develop gradually, so many people may have it for years without noticeable symptoms.”
What causes insulin resistance?
Insulin resistance doesn’t typically point to a single cause. Instead, it’s often a mix of genetic, lifestyle and underlying health conditions.
A family history of Type 2 diabetes, gestational diabetes or increasing age — especially after 35 — can increase your risk. But many of the drivers are tied to everyday habits and overall health, including:
Obesity
Carrying excess body fat — especially around the abdomen — is closely linked to insulin resistance. Abdominal fat releases substances that interfere with how insulin works in the body.
Poor diet
Eating a lot of refined carbohydrates, drinking sugary drinks and taking in too many calories cause repeated blood sugar spikes. Over time, this forces your pancreas to produce increasing amounts of insulin to keep levels stable.
Sedentary lifestyle
Low physical activity and long periods of sitting reduce how efficiently your muscles use glucose, which contributes to higher blood sugar.
Lack of sleep
Regularly getting fewer than 7 hours of sleep can disrupt hormones that regulate appetite and stress — both of which can affect insulin sensitivity.
Chronic stress
Prolonged stress keeps cortisol levels elevated. This raises blood sugar and makes it harder for your body to respond properly to insulin.
Smoking
Nicotine from cigarettes and e-cigarettes triggers a stress response in the body, which can reduce insulin sensitivity over time.
Certain medications
Some medications, like steroids, antidepressants and blood pressure drugs, can cause insulin resistance.
PCOS and other conditions
Conditions like polycystic ovary syndrome (PCOS), obstructive sleep apnea, fatty liver disease, and Cushing’s syndrome are all associated with reduced insulin sensitivity due to underlying hormonal and metabolic changes.
“You can’t change all insulin resistance and prediabetes risk factors like family history and age,” says Dr. Gupta. “But you can take steps to reduce your risk and even reverse the condition to improve your long-term health.”
Signs of insulin resistance
Insulin resistance often has no obvious symptoms at first. Many people only discover it through routine blood work or evaluation for another condition.
Early signs of insulin resistance can include:
- Elevated fasting glucose (100 – 125 mg/dL may suggest prediabetes)
- Lipid profile showing high triglycerides with low HDL (“good”) cholesterol
- Larger waist circumference
- Dark, velvety patches of skin on the neck, armpits or groin (acanthosis nigricans)
As insulin resistance progresses, you may notice prediabetes or diabetes symptoms, such as increased hunger and thirst, frequent urination and fatigue.
“Left untreated, insulin resistance increases the risk of Type 2 diabetes, nonalcoholic fatty liver disease, high blood pressure, heart disease, sleep apnea and PCOS,” says Dr. Gupta. “Because these conditions can progress silently, regular screening and follow-up are important if you have risk factors.”
What you can do to help reverse insulin resistance
By making lifestyle changes — and taking medication, if your doctor recommends it — you can take steps toward reversing insulin resistance and preventing progression to diabetes.
Healthy lifestyle habits
Focusing on daily habits can have a powerful impact on insulin sensitivity:
- Reduce calories in your diet to lose weight, if appropriate.
- Eat more nutrient-dense and high-fiber foods, such as fruits, vegetables, whole grains, low-fat dairy and healthy fats.
- Limit refined carbs and ultra-processed foods, which tend to be high in added sugars and low in nutrition.
- Aim for at least 150 minutes of moderate-intensity aerobic activity each week (like brisk walking, cycling or swimming), plus 2 or more days of strength training
- Try to get 7 to 9 hours of sleep each night.
- Incorporate stress-management techniques (like yoga, mindfulness or breathing exercises).
“Many people find success reversing prediabetes through a combination of weight loss, improved fitness and dietary changes,” says Dr. Gupta. “Even a 5% to 10% reduction in body weight can significantly improve how the body responds to insulin.”
Medical treatments
Sometimes, medication along with lifestyle changes is necessary — especially if your blood sugar remains elevated.
FDA-approved Metformin (Glucophage) is often the first-choice drug to manage blood sugar, improve insulin sensitivity and prevent Type 2 diabetes. If you need help losing weight, weight-loss drugs also may be considered.
Your provider may also recommend medication to treat coexisting conditions, such as high blood pressure, high cholesterol or PCOS, that can lead to insulin resistance.
“With early detection and ongoing management, many people have improved energy, better blood sugar control and lower risk of complications,” says Dr. Gupta.
“Even if you can’t permanently defeat insulin resistance, you can help your body respond to it more effectively and improve long-term health.”
Next steps:
Learn about diabetes care at Geisinger
Find out natural ways to boost your GLP-1 hormone
Warning signs you may have diabetes