What Is the Main Cause of Insulin Resistance?

The most common causes of insulin resistance are excess body fat, especially the deep fat around your belly and organs, and not enough physical activity. These two factors are the ones most consistently linked to insulin resistance in research. Genetics, age, certain medications, and some hormone conditions also play a role.

But naming belly fat and inactivity as the cause leaves out an important question: why are they there in the first place? For many people, the answer includes stress their body is under that they do not recognize as stress. Short or broken sleep, years of emotional strain, ongoing inflammation, digestive problems, and blood sugar swings all raise stress hormones such as cortisol. Cortisol works against insulin directly, and it also signals your body to store fat around your middle. This is why eating less and exercising more often stalls. The drivers underneath are still active.

In most people, insulin resistance does not have one cause. It builds from several factors that feed each other. Finding which ones are active in your body is what makes a plan to reverse it work.

Key Points

  • Belly fat and inactivity are the most common causes: Excess visceral fat and lack of physical activity are the two factors most strongly linked to insulin resistance.

  • Visceral fat is hormonally active: The deep fat around your organs releases substances that interfere with how insulin works, which is why belly fat matters more than fat elsewhere.

  • Stress is a hidden driver: Cortisol and adrenaline counteract insulin, and chronic stress also promotes belly fat storage.

  • Sleep loss causes insulin resistance on its own: In a 2024 randomized trial, cutting sleep by about 90 minutes a night for six weeks raised insulin resistance in women, independent of weight changes.

  • Diet quality matters: A diet heavy in highly processed foods, refined carbohydrates, and sugary drinks is linked to insulin resistance.

  • Some causes cannot be changed: Genetics, family history, and age raise your risk.

  • Medications and medical conditions can cause it: Steroids, some blood pressure medications, some antipsychotics, some HIV treatments, low thyroid function, Cushing syndrome, PCOS, and sleep apnea are all linked to insulin resistance.

  • Most people have more than one driver: The causes reinforce each other, so addressing only one often is not enough.

Understanding Insulin Resistance

Insulin is a hormone made by your pancreas. It moves glucose (sugar) from your blood into your cells, where it is used for energy or stored. Insulin resistance means the cells in your muscles, fat, and liver stop responding well to insulin. Your pancreas makes more insulin to keep blood sugar in range. As long as it can keep up, blood sugar stays normal and you usually have no symptoms.

Over time, the pancreas can struggle to keep up, and blood sugar starts to rise. Blood sugar that is higher than normal but not high enough to be called diabetes is prediabetes. Without changes, prediabetes can progress to type 2 diabetes.

Insulin resistance tends to build on itself. High insulin levels make it easier to store fat around your middle. More belly fat worsens insulin resistance. Worse insulin resistance pushes insulin higher. Stress, poor sleep, and inactivity feed into this loop at several points. This is why the cause is rarely a single factor and why the loop has to be interrupted from more than one side.

The Causes of Insulin Resistance, Explained

Excess belly fat

Excess body fat is considered a primary cause of insulin resistance, and visceral fat, the deep fat that wraps around your liver, pancreas, and intestines, raises the risk most. Visceral fat is metabolically active. It responds strongly to hormones and releases substances that interfere with insulin signaling. That is why two people with the same weight can have very different levels of insulin resistance depending on where they carry their fat.

Physical inactivity

Movement makes your cells more sensitive to insulin, and muscle is one of the main places your body uses blood sugar. When you are inactive, muscle takes up less glucose, and insulin has to work harder. Long periods of sitting add to the problem even in people who exercise at other times.

Hidden stress

Stress is one of the most overlooked causes of insulin resistance. When your body is under stress, it releases cortisol and adrenaline to raise blood sugar so you have fuel to respond. Those hormones counteract insulin. In a short emergency, that is useful. When stress is constant, it keeps insulin from working well day after day. A review of the research found that chronic stress can impair insulin action through several pathways, including stress hormones, the nervous system, and inflammation. The same review notes that stressful life events, workplace stress, and disturbed sleep are linked to insulin resistance.

Many of the stressors that matter most are not the ones people think of as stress:

  • Short or broken sleep

  • Years of emotional strain: work pressure, caregiving, grief, or difficult relationships

  • Ongoing inflammation

  • Digestive problems that keep your body in a low-grade state of stress

  • Blood sugar swings from skipped or unbalanced meals

  • Under-recovery: hard workouts or under-eating without enough rest

Cortisol also signals your body to store visceral fat. This means stress can drive insulin resistance directly and also through the belly fat it helps build.

Poor sleep

Sleep deserves its own mention because the evidence is direct. In a 2024 randomized trial published in Diabetes Care, healthy women who cut their sleep by about 90 minutes a night for six weeks became more insulin resistant, with stronger effects in postmenopausal women. The effect was largely independent of weight changes. When the women returned to their usual sleep, their insulin and glucose levels returned to normal. Sleep apnea, a condition that repeatedly interrupts breathing during sleep, is also a known risk factor.

Diet quality

A diet built on highly processed foods, refined carbohydrates, and sugary drinks is linked to insulin resistance. These foods cause sharp rises in blood sugar that require large amounts of insulin to bring back down, and they make it easier to gain belly fat. The pattern of eating also matters. Skipping meals and then overeating creates the blood sugar swings described above.

Genetics, family history, and age

Some people are more likely to develop insulin resistance because of their genes. Having a parent or sibling with prediabetes or type 2 diabetes raises your risk, and so does getting older. These factors cannot be changed, but they do not decide the outcome on their own. They lower the threshold at which the changeable causes start to matter.

Medications

Some medications can cause insulin resistance, including steroids, some blood pressure medications, some antipsychotics, and some HIV treatments. A short course of steroids can cause temporary insulin resistance. If you take a medication that may contribute, do not stop it on your own. Talk with your prescribing provider about whether it is playing a role.

Hormone and medical conditions

  • Low thyroid function (hypothyroidism): Slows metabolism and can lead to insulin resistance.

  • Cushing syndrome: A rare condition with excess cortisol, which directly counteracts insulin.

  • Polycystic ovary syndrome (PCOS): Closely linked to insulin resistance.

  • Acromegaly: A rare condition with high growth hormone levels.

  • A history of gestational diabetes: Raises the long-term risk.

How Agape looks for the cause

At Agape Integrative Medicine, the first step is understanding your full health story: when your energy, weight, or cravings started to change, what you have already tried, and what is happening with your sleep, stress, digestion, and medications. Laboratory testing, including blood chemistry, thyroid testing, and metabolic markers, is used when it helps answer a specific question. The goal is to identify which drivers are active in your body, not to assume everyone’s insulin resistance comes from the same place. From there, you get a personalized plan and an explanation of why each recommendation is being made. If you want help finding what is driving your insulin resistance, you can book a new patient appointment.

Who It’s For and Who Should Be Cautious

This information is most useful for adults who have been told they have insulin resistance or prediabetes, have a family history of type 2 diabetes, or have tried eating less and exercising more without lasting results. It is also relevant for people with PCOS, sleep apnea, a history of gestational diabetes, or long-term stress they suspect is affecting their health. People who want to understand why their body is responding this way tend to do well with Agape’s functional medicine approach.

Some caution applies. Insulin resistance can look like other conditions, and fatigue, weight gain, and cravings have many possible causes, including thyroid problems, anemia, and depression. These should be evaluated rather than assumed. If a medication you take may be contributing, the benefits of that medication usually still matter, so any change should be decided with your prescribing provider. If you already have type 2 diabetes or take medication that lowers blood sugar, addressing the causes still helps, but it works alongside your medical care, not in place of it.

Risks, Side Effects, and Monitoring

When the causes of insulin resistance are left in place, the risk of prediabetes, type 2 diabetes, metabolic syndrome, fatty liver disease, and heart disease rises over time. Not everyone with insulin resistance develops these complications, but addressing the drivers early improves the outlook.

Changes aimed at the causes are generally safe, but they have trade-offs. People taking glucose-lowering medications can develop low blood sugar when they change their diet, exercise more, or sleep better, and their doses may need adjusting. Starting exercise too quickly can cause injury. Aggressive calorie cutting can cost muscle, which works against insulin sensitivity. Supplements marketed for blood sugar or cortisol can interact with prescription medications and should be reviewed with your provider.

Tracking progress over time shows whether the right causes are being addressed. Fasting glucose, A1C, and cholesterol and triglyceride levels, rechecked at reasonable intervals, show which direction your metabolism is heading. Changes in your waist measurement, energy after meals, cravings, and sleep quality are also useful, and they often improve before labs do.

These are individualized decisions best made with a knowledgeable provider. Medications should not be started, stopped, or combined without guidance from the provider who prescribes them.

Safety

See a medical provider promptly if you notice increased thirst, frequent urination, increased hunger, blurred vision, unexplained weight loss, frequent infections, or sores that heal slowly. These can be signs that blood sugar is already high or that diabetes has developed.

If you take a medication that lowers blood sugar and you feel shaky, sweaty, confused, or notice a racing heartbeat, you may have low blood sugar. Follow your provider’s instructions for treating it. Call 911 if someone becomes severely confused, has a seizure, or cannot respond.

Rapid weight gain in your face, upper back, and abdomen, along with purple stretch marks, easy bruising, or muscle weakness, needs medical evaluation for hormonal causes such as excess cortisol.

Loud snoring, gasping or choking during sleep, or heavy daytime sleepiness should be evaluated for sleep apnea.

If stress, low mood, or anxiety feels unmanageable, reach out to a mental health professional. That support is part of addressing a real cause of insulin resistance. If you are in crisis in the U.S., call or text 988 for the Suicide & Crisis Lifeline, or call 911.

Do not stop or change any prescribed medication on your own.

Sources and Citations

Reviewed By Dr. Jordan Robertson, DC
Last updated: October 2026