Most people associate heart disease with cholesterol. LDL cholesterol rises, plaque builds, and arteries narrow. That model is not wrong, but it is incomplete. Beneath many cases of cardiovascular disease is a deeper metabolic issue: insulin resistance.
Insulin resistance does not just affect blood sugar. It alters vascular function, lipid metabolism, inflammation, and clotting, often years before diabetes develops.
What is Insulin Resistance?
Insulin is a hormone that helps move glucose from the bloodstream into cells. In insulin resistance, the body becomes less responsive to insulin’s signal. To compensate, the pancreas produces more insulin. Over time, this leads to impaired glucose control, abnormal lipid metabolism, increased inflammation, and vascular dysfunction.
Importantly, this process can occur even when fasting glucose is normal. This is why insulin resistance can develop and progress silently before showing up on standard lab work.
How Insulin Resistance Increases Cardiovascular Risk
Insulin resistance is not just a precursor to diabetes. It is an independent driver of cardiovascular disease. Higher levels of insulin resistance are associated with increased risk of coronary heart disease and cardiovascular events, even in individuals with normal blood sugar (Gast et al., 2012; Wang et al., 2022). This means cardiovascular damage often begins well before diabetes is diagnosed.
How Insulin Resistance Affects the Cardiovascular System
Endothelial Dysfunction
Healthy blood vessels rely on nitric oxide to regulate blood flow. Insulin normally stimulates nitric oxide production through the PI3K/Akt pathway. In insulin resistance, this pathway is impaired, while compensatory hyperinsulinemia promotes vasoconstriction and inflammation through alternative signaling pathways (Mechanick et al., 2020).
The result is reduced vascular flexibility and increased stress on the arterial wall.
Atherogenic Dyslipidemia
Insulin resistance reshapes lipid metabolism into a pattern strongly associated with cardiovascular risk. This includes elevated triglycerides, low HDL cholesterol, and an increase in small, dense LDL particles. These particles are more likely to penetrate the arterial wall, become oxidized, and contribute to plaque formation (Ormazabal et al., 2018).
Chronic Inflammation and Oxidative Stress
Insulin-resistant adipose tissue becomes metabolically active and releases inflammatory cytokines such as TNF-α and IL-1β. These signals promote vascular inflammation, recruit immune cells into the arterial wall, and accelerate plaque development (Mechanick et al., 2020).
Prothrombotic State
Insulin resistance increases clotting tendency through multiple mechanisms, including increased platelet activation, elevated fibrinogen, and reduced fibrinolysis (Ormazabal et al., 2018). This contributes to increased risk of acute cardiovascular events such as heart attack and stroke.
Blood Pressure and Vascular Tone
Insulin resistance contributes to elevated blood pressure through reduced nitric oxide availability, increased sympathetic nervous system activity, and activation of the renin-angiotensin-aldosterone system (Reaven et al., 1996). These changes increase vascular resistance and further strain the cardiovascular system.
Cardiac and Metabolic Dysfunction
At the cellular level, insulin resistance disrupts how the heart uses energy. The myocardium loses metabolic flexibility and becomes less efficient, contributing to oxidative stress and long-term cardiac dysfunction (Ormazabal et al., 2018).
How to Identify Insulin Resistance
Insulin resistance is often missed because glucose levels may remain normal for years.
Laboratory Markers
Useful surrogate markers include:
- Triglyceride-to-HDL ratio
- Triglyceride-glucose (TyG) index
The TyG index has strong diagnostic performance with high sensitivity and specificity. Additional markers include lipid accumulation product and TyG-BMI (Mazidi et al., 2018; Er et al., 2016).
Clinical Clues
Common signs of insulin resistance include abdominal obesity, elevated triglycerides, low HDL cholesterol, hypertension, and family history of type 2 diabetes (Sperling et al., 2015; Eckel et al., 2005). Skin findings such as acanthosis nigricans and skin tags may also be present.
How to Improve Insulin Resistance
Insulin resistance is highly responsive to lifestyle interventions.
Dietary Patterns
Several dietary approaches improve insulin sensitivity, including Mediterranean, low-carbohydrate, and low-glycemic index diets (Ajala et al., 2013; Shai et al., 2008; Liu et al., 2025).
Fiber Intake
Increasing dietary fiber improves glycemic control and reduces insulin resistance (Jovanovski et al., 2019; Weickert & Pfeiffer, 2018).
Meal Timing
Time-restricted eating improves insulin sensitivity, even in the absence of weight loss (Sutton et al., 2018; Cienfuegos et al., 2022).
Food Order
Consuming protein and vegetables before carbohydrates can significantly reduce post-meal glucose and insulin responses (Shukla et al., 2019; Imai et al., 2014).
Exercise
Both aerobic and resistance training improve insulin sensitivity, increase glucose uptake, and reduce HbA1c levels (Colberg et al., 2016; Kanaley et al., 2022).
The Bigger Picture
Cardiovascular disease is not just about cholesterol. It reflects the interaction between lipids, inflammation, vascular function, and metabolism. Insulin resistance sits at the center of this network and contributes to multiple pathways involved in atherosclerosis and cardiometabolic disease (Mechanick et al., 2020; Kosmas et al., 2023).
Bottom Line
Insulin resistance can develop years before abnormal glucose levels appear. It contributes to atherosclerosis, vascular dysfunction, and cardiovascular risk independently of diabetes.
Addressing insulin resistance early through nutrition, lifestyle, and targeted interventions is one of the most effective strategies for long-term cardiovascular health.
About the Author
Joseph Lehrberg, MS, RD is a registered dietitian specializing in cardiovascular and metabolic health and founder of CardioFunction Integrative Nutrition Services, a nutrition practice based in Boston. He works with patients with elevated cholesterol, high coronary artery calcium scores, high triglycerides, statin intolerance, and other cardiometabolic risk factors to develop evidence-based nutrition strategies for long-term heart health.
Learn more about working with him here.
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