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Insulin resistance and prediabetes are conditions that arise when the body does not effectively utilize insulin. To understand these conditions, it’s crucial to first grasp the fundamental role of insulin in our bodies.
Delving into Insulin: What Is It?
Insulin is a vital hormone produced by the pancreas, an organ located behind the stomach. Its primary function is to regulate blood sugar, or glucose, levels. Glucose is the body’s main source of energy, derived from the food we consume. When you eat, your digestive system breaks down carbohydrates into glucose, which then enters your bloodstream. Insulin acts as a key, allowing glucose to enter cells throughout your body – particularly in muscle, fat, and liver tissues – where it can be used for immediate energy or stored for later use.
The pancreas plays a crucial role in this process. After a meal, as blood glucose levels rise, the pancreas responds by releasing insulin into the bloodstream. This insulin then facilitates the uptake of glucose by cells, effectively lowering blood sugar levels and maintaining them within a healthy range. The liver also contributes to glucose regulation by producing glucose and releasing it into the bloodstream when needed, such as during fasting periods or between meals. Insulin signals the liver to stop producing glucose when it’s not needed, further helping to balance blood sugar.
Alt text: Illustration showing pancreas cells, highlighting their role in insulin production.
Insulin Resistance Explained
Insulin resistance occurs when cells in your muscles, fat, and liver become less responsive to insulin’s signals. Imagine the ‘key’ (insulin) becoming less effective at opening the ‘door’ (cells) to allow glucose in. As a result, glucose accumulates in the bloodstream instead of entering the cells for energy.
To compensate for this resistance, the pancreas works harder to produce more insulin. Initially, this increased insulin production can overcome the reduced sensitivity of cells, and blood glucose levels may remain in the normal range. However, this state of overworking the pancreas is not sustainable in the long term.
Prediabetes: A Warning Sign
Prediabetes is a condition where blood glucose levels are higher than normal but not yet high enough to be classified as type 2 diabetes. It often develops in individuals who are already experiencing insulin resistance or when the beta cells in the pancreas, responsible for insulin production, are unable to produce sufficient insulin to maintain normal blood glucose levels.
In prediabetes, the body struggles to move glucose from the bloodstream into cells effectively. This results in elevated blood sugar levels. Prediabetes is a significant health concern because it greatly increases the risk of developing type 2 diabetes, as well as other health problems like heart disease and stroke, over time if left unaddressed.
How Widespread is Prediabetes?
Prediabetes is a widespread health issue. In the United States alone, over 84 million adults aged 18 and older have prediabetes. This means that approximately 1 in 3 adults in the U.S. are living with prediabetes. This high prevalence underscores the importance of understanding prediabetes and taking steps to prevent its progression to type 2 diabetes.
Who is at Higher Risk?
Certain factors increase the likelihood of developing insulin resistance and prediabetes. These risk factors can be broadly categorized into genetic and lifestyle-related factors. Individuals with one or more of the following risk factors are more susceptible:
- Overweight or Obesity: Excess weight, particularly abdominal fat, is strongly linked to insulin resistance.
- Age 45 or Older: The risk of prediabetes increases with age.
- Family History of Diabetes: Having a parent, sibling, or child with diabetes increases your risk.
- Certain Ethnicities: African Americans, Alaska Natives, American Indians, Asian Americans, Hispanic/Latinos, Native Hawaiians, and Pacific Islander Americans have a higher prevalence of prediabetes.
- Physical Inactivity: A sedentary lifestyle contributes to insulin resistance.
- Health Conditions: High blood pressure and abnormal cholesterol levels are associated with increased risk.
- History of Gestational Diabetes: Diabetes during pregnancy increases the future risk of type 2 diabetes and prediabetes.
- History of Heart Disease or Stroke: Cardiovascular disease is linked to insulin resistance.
- Polycystic Ovary Syndrome (PCOS): Women with PCOS have a higher risk of insulin resistance and prediabetes.
- Metabolic Syndrome: This cluster of conditions including high blood pressure, abnormal cholesterol, and excess abdominal fat significantly increases prediabetes risk.
While some risk factors like genetics, age, and ethnicity are not modifiable, lifestyle factors such as diet, physical activity, and weight management can be changed to reduce the risk of insulin resistance and prediabetes.
Alt text: Image depicting waist circumference measurement, highlighting abdominal obesity as a risk factor for insulin resistance.
Unraveling the Causes
The exact causes of insulin resistance and prediabetes are still being researched, but excess weight and physical inactivity are considered major contributing factors.
The Role of Excess Weight
Obesity, especially excess fat in the abdomen and around organs (visceral fat), is strongly implicated in insulin resistance. A waist circumference of 40 inches or greater for men and 35 inches or greater for women is associated with increased insulin resistance, even in individuals with a normal Body Mass Index (BMI). Research indicates that visceral fat is not merely for energy storage; it also releases hormones and other substances that can promote chronic inflammation in the body. This inflammation is believed to play a significant role in insulin resistance, type 2 diabetes, and cardiovascular disease. Furthermore, excess weight and insulin resistance can contribute to the development of nonalcoholic fatty liver disease.
The Impact of Physical Inactivity
Lack of regular physical activity is another key factor linked to insulin resistance and prediabetes. Regular exercise improves the body’s sensitivity to insulin, making it more efficient at regulating blood glucose levels. Physical activity helps muscles use glucose for energy and improves insulin sensitivity, contributing to better blood sugar control.
Recognizing the Symptoms
Insulin resistance and prediabetes often develop without noticeable symptoms, particularly in the early stages. However, some individuals with prediabetes may experience subtle signs such as darkened skin patches, particularly in the armpits, groin, and on the back and sides of the neck (acanthosis nigricans). Skin tags, small fleshy growths, may also appear in these areas.
Although overt symptoms are usually absent, research suggests that some individuals with prediabetes may already exhibit early signs of eye damage (retinopathy), a complication more commonly associated with diabetes.
Diagnosis: Identifying Prediabetes
Doctors diagnose prediabetes using blood tests. While specific tests for insulin resistance exist, they are complex and primarily used for research purposes. For routine diagnosis of prediabetes, healthcare providers rely on blood glucose tests.
Alt text: Doctor explaining blood test results to a patient, emphasizing the role of blood tests in prediabetes diagnosis.
The most common blood tests used to diagnose prediabetes are:
- Fasting Plasma Glucose (FPG) Test: This test measures blood glucose levels after an overnight fast (at least 8 hours of not eating).
- A1C Test: The A1C test reflects average blood glucose levels over the past 2 to 3 months. It measures the percentage of hemoglobin (a protein in red blood cells) that is glycated, meaning glucose is attached to it.
- Oral Glucose Tolerance Test (OGTT): The OGTT measures blood glucose levels before and 2 hours after drinking a special sugary drink. This test shows how the body processes glucose over time.
The A1C test is convenient but may be less sensitive than the OGTT in detecting prediabetes in some individuals. The OGTT can identify how the body handles glucose after eating, sometimes revealing glucose abnormalities before fasting blood glucose levels become elevated. OGTT is frequently used to screen for gestational diabetes during pregnancy.
Individuals with prediabetes have a significant chance of progressing to type 2 diabetes within 5 to 10 years if no lifestyle changes are made.
The diagnostic ranges for prediabetes are:
- A1C: 5.7 to 6.4 percent
- FPG: 100 to 125 mg/dL (milligrams per deciliter)
- OGTT: 140 to 199 mg/dL
Screening for prediabetes is recommended for individuals who are overweight or obese and have one or more additional diabetes risk factors, or for anyone at age 45 and older. Even with normal test results, repeat testing every 3 years is advised for those with ongoing risk factors.
Prevention and Reversal Strategies
Lifestyle modifications, particularly increasing physical activity and losing weight if needed, can significantly improve insulin sensitivity and help prevent or reverse insulin resistance and prediabetes.
Small, sustainable changes can make a big difference. Adopting healthier eating habits and incorporating more physical activity into daily routines can be effective in reversing insulin resistance and preventing or delaying the onset of type 2 diabetes in people with prediabetes.
Alt text: Image of a person selecting fresh vegetables at a market, highlighting the importance of healthy food choices in preventing insulin resistance and prediabetes.
The Diabetes Prevention Program (DPP), a major research study funded by the National Institutes of Health, demonstrated that for individuals at high risk of developing diabetes, losing 5 to 7 percent of their starting weight through diet and exercise reduced their risk of developing diabetes significantly. For a person weighing 200 pounds, this translates to a weight loss of just 10 to 14 pounds.
The DPP study also showed that metformin, a medication commonly used to treat type 2 diabetes, could delay the onset of diabetes, particularly in younger adults, women with a history of gestational diabetes, and individuals with obesity. Consult your doctor to determine if metformin is appropriate for you.
Creating a plan, tracking progress, and seeking support from healthcare professionals, family, and friends are crucial for making lasting lifestyle changes to prevent or reverse insulin resistance and prediabetes. Lifestyle change programs, such as the National Diabetes Prevention Program, offer structured support and guidance.
Clinical Trials: Advancing Research
The National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK) and other components of the National Institutes of Health (NIH) actively conduct and support research into various diseases and conditions, including insulin resistance and diabetes.
Participating in Clinical Trials
Clinical trials are essential for medical progress. They explore new approaches to prevent, detect, and treat diseases. Researchers also use clinical trials to improve the quality of life for individuals living with chronic conditions. If you are interested in learning more about clinical trials and whether they might be right for you, resources are available to help you make an informed decision.
Finding Open Clinical Trials
To find clinical trials that are currently recruiting participants, you can visit ClinicalTrials.gov. This website provides a searchable database of clinical trials being conducted around the world.
References
Original article references would be listed here if available in the source.
Last Reviewed May 2018
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This content is provided as a service of the National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK), part of the National Institutes of Health.
The NIDDK would like to thank Rita Basu, M.D., University of Virginia School of Medicine
