About 84 million Americans — more than one in three adults — have a disorder that greatly increases their risk for two potentially lethal diseases: type 2 diabetes and cardiovascular disease (CVD), the leading killer of men and women, often from heart attacks and strokes. Although this disorder, prediabetes, can easily be detected with a blood test covered by almost all health plans, 90% of those with this extremely common blood sugar abnormality (about 75.5 million Americans) are unaware of their peril, according to the CDC.

Yet with early diagnosis and simple lifestyle changes, prediabetes can be reversed in up to 85% of cases without medication, large studies have shown. Here’s a closer look at this often undiagnosed cardiovascular threat, how to find out if you have it, and what you can do to prevent or reverse it.

The Hidden Cause of Most Heart Attacks

It’s very common for people to be diagnosed with prediabetes or diabetes after they’ve suffered a cardiovascular event. In one large study of people treated in the emergency room for a heart attack, 20% were known diabetics. When the other patients were given blood tests, 65% had abnormal blood sugar levels, with half having previously undiagnosed diabetes and the other half meeting criteria for prediabetes.

Patients often chalk this double whammy up to bad luck, believing they have been hit with two unrelated diseases at once. Some even wonder if their heart attack somehow triggered their blood sugar disease. Actually, most heart attacks and type 2 diabetes have the same root cause: insulin resistance (IR), an inflammatory disorder in which the body becomes insensitive to insulin, a hormone that helps our cells use glucose for energy.

IR forces beta cells in the pancreas to pump out more and more insulin, trying to keep up with demand. Eventually the beta cells become exhausted and blood sugar starts to rise, starting a slow march toward type 2 diabetes. If prediabetes goes untreated, a cascade of harmful effects occur, affecting all of the body’s arteries. Because insulin resistance is an inflammatory disorder, it makes it easier for white blood cells and cholesterol to penetrate the blood-vessel lining and clump into plaque.

Once arterial disease develops, other biochemical changes sparked by IR further weaken the arterial lining, increasing the risk of a plaque rupture that could lead to a heart attack or stroke. Compounding the cardiovascular danger, people with IR are more prone to developing blood clots. That means if a plaque rupture happens, the resulting clot is likely to be bigger and more likely to trigger a more massive heart attack or stroke.

The No. 1 Warning Sign of Insulin Resistance

Because IR doesn’t cause any noticeable symptoms, it often goes undiagnosed until people develop diabetes. However, there are several tip-offs that you might have it. The leading indicator is a large waistline (above 40 inches for a man and above 35 inches for a woman). Being overweight (a body mass index or BMI of 25 or more) is also a major risk factor for becoming insulin-resistant. Other potential indicators that you may be insulin resistant include the following:

  • Your lipid levels. Surprisingly, people with IR usually don’t have high LDL (bad) cholesterol. Instead, they often have high triglycerides (TG) and low levels of HDL (good) cholesterol.
  • A family history of diabetes or CVD. Not only is a family history of diabetes a powerful indicator of risk for IR, but having relatives who developed CVD at an early age can also be a warning sign, given that IR is the root cause of about most heart attacks and strokes.
  • High blood pressure. Biochemical changes caused by IR can cause arteries to become narrower and less flexible, explaining why people with insulin resistance often develop high blood pressure.
  • Lack of sleep. A recent study found that sleeping fewer than six hours a night triples the risk for prediabetes.
  • Periodontal (gum) disease. Research suggests a two-way link: Periodontal disease worsens IR, and having IR raises risk for developing gum disease.
  • Your age. Because diabetes is more common in middle-aged and older people, the American Diabetes Association (ADA) advises starting screening at age 45, or at a younger age if you have risk factors, such as obesity, physical inactivity or a family history of diabetes,
  • Your ethnicity. Rates of diabetes and IR are higher in African-Americans, Hispanic-Americans, Native Americans, Asian Americans, and Pacific Islanders.
  • Your medical history. Your risk for IR is higher if you have certain medical conditions, including erectile dysfunction, polycystic ovary syndrome (PCOS) or a history of gestational diabetes (high blood sugar during pregnancy).

The Best Test to Check for Prediabetes

The BaleDoneen Method recommends the two-hour oral glucose tolerance test (OGTT), a blood test which the ADA has called “ the gold standard” in screening for problematic blood sugar levels. Covered by almost all health plans, the OGTT involves drinking a sugary liquid after an overnight fast. Blood samples are taken one and two hours later to measure glucose levels, with a level of 140 to 200 mg/dL being diagnostic of prediabetes and one above 200 indicating diabetes.

Many medical providers, however, use an unreliable screening test called hemoglobin A1C. Because it doesn’t require fasting before the blood is drawn, it’s convenient for busy patients. However, the results can frequently be misleading, as a BaleDoneen study presented at the 4th International Congress on Prediabetes and Metabolic Syndrome recently revealed.

The study found that of 527 patients whose blood sugar was checked with various tests, using the A1C test alone would have missed 63% of those with prediabetes! Additionally, the study also demonstrated that 27% of those classified by the A1C test as having prediabetes actually had normal blood sugar when measured by the highly accurate OGTT.

This alarmingly high error — and published data from other researchers with similar findings — are why we recommend against the A1C test. We also recommend against another commonly used screening test known as the fasting plasma glucose test, which has also been shown to be unreliable for diagnosing prediabetes, the earliest and most easily treatable form of blood sugar disease.

How to Avoid or Reverse Prediabetes — Without Medication

About 90% of people who develop prediabetes/IR are overweight with a sedentary lifestyle. If you fit that description, here’s what you need to know: Lifestyle changes can dramatically reduce your risk for IR — and in many cases, can even reverse the disease if you already have it.

In a recent study of more than 3,000 prediabetic people, those who lost 10% of their body weight through a healthy diet and exercising 150 minutes a week reduced their risk for developing full-blown diabetes by 85%. Even modest weight loss had powerful benefits, since those who shed 5% to 7% of their body weight lowered their risk by 54%. Without lifestyle modification or other treatments, many people with prediabetes will progress to full-blown disease within 10 years.

To keep your heart — and pancreas — healthy, we advise cutting down on TV and other screen time and spending a minimum of 22 minutes exercising daily. Check with your medical provider about which activities are most appropriate for you. Also check out our blog post about the best exercises to reduce your waistline and heart attack risk,

An easy first step to counteracting the harmful effects of a sedentary lifestyle is to take short activity breaks from sitting: A recent study found that even among people who spent most of their day parked in a chair, those who took the most activity breaks — even ones as brief as one minute at a time — had, on average, thinner waists (by nearly two inches) and lower levels of inflammatory markers, triglycerides and blood sugar. That’s powerful motivation to rise up and move more!