Although I was not overweight, let alone obese, I had prediabetes long before I developed type 2 diabetes.

Or, as it was then called, impaired glucose tolerance.

With a family history of diabetes, I had failed a glucose tolerance test at 23. When I became pregnant in my 30s, I twice developed gestational diabetes, followed, a few years later, by full-blown type 2.

A new study reveals that I might not have been that unusual.

While being overweight or obese has long been associated with type 2 diabetes, one-third of normal-weight people may have prediabetes, according to a new study published in the Annals of Family Medicine.

The study found that the prevalence of prediabetes increased markedly in the 24 years from 1988 to 2012 among individuals with a body mass index in the healthy range (18.5 to 24.99).

But because normal-weight individuals aren't recognized as being at risk, they often fly under the radar.

"People with prediabetes aren't being detected and treated," says Arch Mainous III, chair of the Health Services Research, Management & Policy department at the University of Florida and lead author of the study. "We need to change how we see the patient population who walks into the office, so we don't see that the only risk factor that drives a doctor to screen is overweight or obesity."

Current guidelines from the U.S. Preventive Services Task Force recommends screening for adults 40 to 70 who are overweight or obese. The American Diabetes Association calls for everyone over age 45 to be screened, because age is a risk factor for diabetes.

Mainous estimates that by following current government recommendations for screening, doctors are missing six million to seven million patients who might not be metabolically healthy. His findings are bolstered by a new study from Northwestern University that finds that doctors following the latest government screening guidelines missed 55 percent of high-risk individuals with prediabetes or diabetes.

According to the CDC, about one in three people in the United States has prediabetes. A diagnosis of prediabetes means having a blood sugar level higher than normal, but not high enough for a diagnosis of diabetes, with a hemoglobin A1C reading - average blood-sugar levels over two to three months - of 5.7 to 6.4 percent.

Without lifestyle changes to improve their health, an estimated 15 percent to 30 percent of people with prediabetes will transition to type 2 diabetes within five years.

People who adopt healthy diet and exercise plans after their diagnosis have a 58 percent of avoiding type 2. However, the lower your hemoglobin A1C number, the lower the risk.

The Florida report analyzed data from the National Health and Nutrition Examination surveys from 1988-1994 and 2009-2012. Researchers found that among healthy-weight adults, age 20 years or older without diagnosed or undiagnosed diabetes, prediabetes increased from 10 percent in 1988-1994 to 19 percent in 2012. Among those 45 years or older, the prevalence of prediabetes increased from 22 percent to 33 percent.

Mark Schutta, medical director of the Penn Rodebaugh Diabetes Center at the University of Pennsylvania, noted that there were a number of factors, including lab errors, hemoglobinopathies (genetic blood disorders), and other conditions such as liver disease that change the binding of glucose to red blood cells, potentially making A1C higher or lower than normal.

"Also, a lot of people don't live in the normal range, but just outside it, and this is inconsequential to their health," Schutta said.

The report arrives during the midst of a nationwide effort by the CDC to alert Americans to the dangers of prediabetes. Some doctors are pushing back on the initiative, saying that it might needlessly alarm patients. Schutta disagrees.

"Thirty million Americans have type 2 diabetes, and 33 percent of Americans will develop diabetes in their lifetimes," he said. "We want to capture people at high risk early. We don't want to dismiss it."

People at high risk include those who have a genetic predisposition to diabetes, who have had gestational diabetes, or are overweight. Additionally, people of African American, South Asian, or Pacific Islander heritage often should be screened before they are 30.

"The number-one killer of diabetics is cardiovascular disease," Schutta said. "For people of normal weight who are stressed by the diagnosis of prediabetes, we can assess their cardiovascular risk. If they're slender, eat a good diet, have a good lipid profile, and are not hypertensive, we'll tell them that they are at low risk for a cardiovascular incident and recheck their A1C every two years.

"And we can tell them that it's unlikely they're going to develop type 2 diabetes," he said.

Another question is whether the cutoff numbers for prediabetes are too low, putting more people in this category.

"We have to draw a line in the sand somewhere," said Kevin Furlong, an endocrinologist and associate professor of clinical medicine at Thomas Jefferson University Hospital in Philadelphia.

"Someone who has a 6.2 or 5.7 is not normal, but is it worth creating anxiety or stress in the patient? If we call it prediabetes, we make people take it more seriously and maybe get them to embark on a healthy lifestyle. Is that a bad thing?" he asked.

"For example, I'll see someone who has a 6.5 hemoglobin A1C, but their fasting blood sugar is normal. But we've found out that if you have a 6.5 you are having perturbations in glucose that can increase retinopathy," a potentially blinding eye condition.

"I see the devastating effects of diabetes on a daily basis," he said. "And who doesn't benefit from adopting a healthier lifestyle? There's no downside to motivating patients to move their body more and eat less. It's something everyone should do."

Patients who are not overweight but are prediabetic should start weight training, Mainous said. Muscle metabolizes sugar in the body better than fat - it's more efficient and requires less insulin.

"For people who don't think they're going to be affected by diabetes, people who are sedentary, people who say, 'I weigh the same as I used to, but I'm soft,' this could be a wake-up call," Mainous said.

"Many times we are looking at people who need to build more muscle rather than losing weight," he said.

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