Up to one-third of healthy weight adults may have prediabetes

A third of adults over the age of 45 who don’t look like they could be at risk for developing diabetes — they’re slender — may actually meet the criteria for prediabetes, according to a University of Florida study.

The findings are cause for concern, the researchers say, because under current guidelines, these individuals would likely not be screened for the condition. The study results appear today (July 11) in the Annals of Family Medicine.

Prediabetes is defined as having blood glucose concentrations higher than normal, but not high enough for a diabetes diagnosis. The condition puts people at higher risk for developing Type 2 diabetes and cardiovascular problems.

“We have an epidemic of diabetes right now and diabetes prevention is a key strategy to try to stem that tide,” said lead investigator Arch G. Mainous III, Ph.D., chair of the department of health services research, management and policy in the UF College of Public Health and Health Professions, part of UF Health. “One of the ways we can do this is to identify people with prediabetes, a high-risk state for development of diabetes, and intervene with drug or lifestyle modifications to keep them from transitioning to diabetes.”

Recommendations from organizations such as the American Diabetes Association and the U.S. Preventive Services Task Force call for prediabetes screenings in individuals who are overweight or obese. The UF research team wanted to learn if using BMI measures alone may be missing people who are considered to be at a healthy weight, but could benefit from prediabetes screening and potential intervention.

In what is believed to be the first study to examine trends in prediabetes prevalence among individuals with a healthy body mass index, the team analyzed data from the National Health and Nutrition Examination Survey, a nationally representative study that uses a combination of interviews and physical examinations. The UF researchers reviewed survey data from 1988 to 1994 and 1999 to 2012, focusing on adults age 20 and older who had a BMI within the healthy weight range — 18.5 to 24.9 — and who did not have a previous diagnosis of diabetes.

The prevalence of prediabetes, categorized by a blood glucose level between 5.7 and 6.4 percent, which the American Diabetes Association considers prediabetes, varied by year, but tended to increase overall. By 2012, 19 percent of adults age 20 to 44 at a healthy weight had a blood glucose reading that met the criteria for prediabetes, and 33 percent of adults age 45 and older in the healthy weight range met the criteria.

“A large proportion of these people will develop diabetes, but we won’t be able to do any diabetes prevention with them because we aren’t looking for them under current screening guidelines,” said Mainous, the Florida Blue endowed chair of health administration.

Mainous is planning a study that will evaluate the cost-effectiveness of screening all adults for prediabetes.

Because carrying more weight in the abdomen has been linked to diabetes and cardiovascular problems, the UF team also evaluated participants’ waist circumference and waist-to-height ratio. While they did find that waistlines of adults at a healthy weight have expanded over time, after adjusting for demographic factors and close relatives having diabetes, the team discovered that an unhealthy waist size did not predict prediabetes.

More research is needed to determine the cause of prediabetes in people who are at a healthy weight, Mainous said. One explanation may be an increase in sedentary lifestyle that could change body composition and lead to a condition known as healthy weight obesity in which people have a BMI within the normal range, but a high proportion of fat to lean muscle. People with healthy weight obesity are more likely to develop metabolic syndrome, which can cause increased blood pressure, high blood sugar and abnormal cholesterol levels.

“We need to shift the paradigm and think about other ways of looking at people rather than just using the BMI cutoffs,” said Mainous, who led a previous study that found that weaker grip strength may indicate undetected diabetes and hypertension. “Hopefully we can move away from focusing solely on calorie restriction and weight loss as diabetes prevention tactics because these people who have prediabetes and are at a healthy weight would be missed.”

Study co-authors included Rebecca Tanner, M.A., a research coordinator, and Ara Jo, M.S., a doctoral student, both in the department of health services research, management and policy, and Stephen Anton, Ph.D., an associate professor and division chief in the UF College of Medicine’s department of aging and geriatric research and a member of the UF Institute on Aging. The study was supported by a grant awarded to Anton from the National Institutes of Health and the National Institute on Aging under award P30AG028740.