The Connection Between Insulin Resistance, Diabetes, and Heart Disease

Blog, Diabetes and Metabolic Health /

In recent decades, the prevalence of insulin resistance, type 2 diabetes, and cardiovascular disease has surged dramatically. These interconnected health issues have profound implications for global public health, making it essential to understand their relationships and how lifestyle changes can mitigate risks. Let’s explore the connection between insulin resistance, diabetes, and heart disease and how you can protect yourself.

The connection between insulin resistance, diabetes, and heart disease
Connecting Insulin Resistance and Heart Disease

Understanding Insulin Resistance

Insulin resistance is a condition where the body’s cells become less responsive to insulin, a hormone produced by the pancreas. Insulin’s job (among other things) is to help regulate blood sugar levels. Imagine insulin as a key that opens the door to cells, allowing glucose inside. In a healthy system, insulin is released from the pancreas in response to a rise in blood sugar, also known as glucose. Insulin easily unlocks the cells to allow glucose to enter and be used for energy.

But when insulin resistance occurs, the locks (cell receptors) become rusty and require more keys (insulin) to open the cell to allow glucose in. Over time, the pancreas produces more insulin to force glucose into the cell to compensate for the resistance. This causes high insulin levels which in turn creates more insulin resistance. Eventually, the pancreas can’t keep up with the increased demand and glucose levels rise. Once the glucose level reaches a certain point, it is called diabetes.  

Development of Insulin Resistance

Unlike type 1 diabetes, type 2 diabetes is not caused by a lack of insulin. In fact, it results from an excess of insulin. Scientists once believed insulin levels rose because cells had become insulin resistant, researchers now believe that insulin levels go up causing cellular insulin resistance. When insulin levels stay high it can contribute to the development of type 2 diabetes as well as cardiometabolic issues.

The next question you may ask is, “what causes high insulin levels?”. The short answer is we don’t know for sure. There are several theories as to the mechanism by which insulin levels rise. Most likely it is a combination of factors combined with certain genetic predispositions that promote the development of insulin resistance and ultimately type 2 diabetes. Let’s look at some factors that have been associated with the development of insulin resistance:

  • Genetics: Family history can predispose individuals to insulin resistance. This may be due to specific gene mutations or alterations in gene expression that more readily promote insulin resistance. Diet and lifestyle can alter how these genes manifest.
  • Obesity: Excess body fat, particularly around the abdomen, can interfere with insulin’s ability to regulate blood sugar. Some research suggests that fat cells can release certain hormones that may interfere with glucose regulation.
  • Sedentary Lifestyle: Physical inactivity reduces the body’s ability to utilize glucose effectively. Exercise helps to improve insulin sensitivity.
  • Poor Diet: Diets high in refined sugars and unhealthy fats can promote insulin resistance. Excess calorie intake leading to obesity and insufficient nutrient intake also play a role.

The Path from Insulin Resistance to Type 2 Diabetes

Insulin resistance precedes the onset of type 2 diabetes. Initially, the pancreas compensates by producing more insulin. But as the resistance worsens, insulin can no longer keep up with the demand and blood sugar levels start to rise. This is known as pre-diabetes. Unfortunately, this is typically the first sign that gets noticed in someone with insulin resistance. Since insulin levels are rarely tested, people aren’t aware of their impaired metabolic health until blood sugar levels become a problem. By this point, insulin resistance may have been an issue for years or even decades. The increase in blood sugar levels indicates your body can no longer compensate. Without intervention, prediabetes can progress to type 2 diabetes, characterized by consistently high blood sugar levels.

This progression from insulin resistance to type 2 diabetes is a major public health concern. According to the CDC, over 38 million Americans (1 in 10 people) have diabetes, with type 2 diabetes accounting for 90-95% of cases. This has become a health and financial nightmare as the rate of type 2 diabetes continues to climb. Unfortunately, as rates of obesity skyrocket, so do rates of diabetes. Research suggests that free fatty acids in the blood trigger insulin release even at normal blood sugar levels. Because the amount of free fatty acids is largely dependent on excess adipose (fat) tissue, this correlates with the increase in obesity and diabetes cases we see.

Impact of Insulin Resistance on the Body

The effects of insulin resistance extend beyond blood sugar regulation. This is why this growing trend is so concerning. High insulin levels may be at least partly to blame for diabetes complications. Here are a few ways insulin resistance causes damage to the body.

  • Blood Vessels: High insulin levels can damage the endothelium (inner lining) of blood vessels, leading to atherosclerosis (hardening and narrowing of the arteries).
  • Blood Pressure: Insulin resistance often coexists with hypertension. The condition makes blood vessels less responsive to normal relaxation signals, contributing to increased blood pressure.
  • Cholesterol Levels: Insulin resistance is associated with dyslipidemia which is defined as having high levels of LDL (frequently referred to as bad) cholesterol and triglycerides and low levels of HDL (known as good) cholesterol.
  • Liver: Excess insulin can lead to non-alcoholic fatty liver disease (NAFLD), as excess glucose is converted into fat and stored in liver cells. This impaired liver function can further hinder metabolic health. Over time, NAFLD can progress to more severe liver damage.
  • Heart: Collectively, these effects increase the risk of cardiovascular diseases, including heart attacks and strokes.

Connecting Insulin Resistance and Cardiovascular Disease

Insulin resistance significantly elevates the risk of cardiovascular disease (CVD). The American Heart Association notes that people with diabetes are twice as likely to have heart disease or a stroke compared to those without diabetes. This connection is driven by the triad of hypertension, hyperlipidemia, and atherosclerosis—all common in insulin resistance.

Hypertension: Hypertension (high blood pressure) often develops due to insulin resistance. The stiffening and narrowing of blood vessels increase the heart’s workload, raising blood pressure. This chronic strain can lead to heart failure or kidney damage over time.

Blood Vessels and Blood Pressure: Insulin resistance can damage the lining of blood vessels, leading to atherosclerosis (hardening of the arteries). This condition contributes to hypertension (high blood pressure), as narrowed arteries increase the pressure needed to pump blood through the body.

Cholesterol Levels: Insulin resistance is often accompanied by an unfavorable lipid profile: elevated levels of triglycerides and LDL (bad cholesterol) and reduced levels of HDL (good cholesterol). This imbalance further accelerates the development of atherosclerosis.

Cardiovascular Disease: The combination of high blood pressure, unhealthy cholesterol levels, and damaged blood vessels sets the stage for cardiovascular diseases. The accumulation of arterial plaque can cause heart attacks or strokes, major causes of mortality worldwide.

Mitigating Risks Through Diet and Lifestyle

The good news is that diet and lifestyle changes can significantly reduce the risk of developing insulin resistance, type 2 diabetes, and cardiovascular disease:

  • Healthy Diet: Focus on whole foods, including fruits, vegetables, whole grains, lean proteins, and healthy fats. Reduce refined carbohydrates, avoid sugary beverages, limit processed foods, and stay away from trans fats. Watch portions to avoid overeating.
  • Regular Exercise: Aim for at least 150 minutes of moderate-intensity aerobic activity each week, along with muscle-strengthening activities on two or more days a week.
  • Weight Management: Maintaining a healthy weight through diet and exercise reduces the strain on your body’s insulin production and improves metabolic health.
  • Stress Reduction: Practices like mindfulness, meditation, and adequate sleep can help manage stress, which is beneficial for metabolic health.
  • Sleep: Ensure adequate quantity and quality sleep to support overall metabolic health.

Conclusion

Understanding the intricate connection between insulin resistance, diabetes, and heart disease underscores the importance of proactive health management. By adopting healthier lifestyle choices, individuals can significantly lower their risk of these chronic diseases, paving the way for a healthier future. As a registered dietitian specializing in metabolic health, I encourage everyone to take small, sustainable steps toward better health—your heart will thank you.

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