For the U.S. population overall, the average BMI is just under 29, according to researchers. A BMI of 25 to 30 is considered overweight, and a BMI of 30 or greater is considered obese. But Asian Americans often develop diabetes at a lower BMI. The American Diabetes Association recommends Asian Americans get tested for diabetes at a BMI of 23 or higher, a lower threshold than the general population. (iStock)

This post has been updated.

More than half of Asian Americans with diabetes don’t know they have the condition, according to new research that quantifies, for the first time, how common Type 2 diabetes is among that minority group in the United States.

What’s even more surprising: Asian Americans have the highest proportion of undiagnosed diabetes among all ethnic and racial groups, at 51 percent, according to researchers from the National Institutes of Health and the Centers for Disease Control and Prevention.

And something else to keep in mind:  Asian Americans may be less overweight, generally, than the rest of the U.S. population, but they may actually be at greater risk for developing diabetes.

Compared to Americans in general, Asian Americans are “not as overweight, but they should still be mindful of their activity levels and their diet and see their doctors to make sure they don’t have diabetes,” said Catherine Cowie, the study’s senior author and director of diabetes epidemiology programs at the National Institutes of Health’s National Institute of Diabetes and Digestive and Kidney Diseases.

“Because at lower weight levels, they actually have a higher risk for diabetes,” she said in an interview.

That’s because Asian Americans often develop diabetes at a lower body mass index, or BMI, than the U.S. population overall. (BMI estimates how much a person should weigh based on their height.)  But it doesn’t address the distribution of fat in a person’s body. Fat around the waist is a risk factor for diabetes and other diseases, research has shown.

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The latest analysis was published this week in the Journal of the American Medical Association. Other studies have found that many Asian Americans have higher blood pressure and more fat than other groups. "That may indicate a propensity to put on fat in the middle part of the body, even though their BMI looks okay,” Cowie said.

Asian Americans who are at risk may not realize it, and as a result, "they don't go to the doctor, and the doctor doesn’t do a blood test to look for diabetes,” she said.

The average BMI for all Asian Americans surveyed was under 25. The American Diabetes Association recommends Asian Americans get tested for diabetes at a BMI of 23 or higher. Here's a handy chart from the National Diabetes Education Program that lists the BMIs that put different races and ethnicities at risk.

Researchers reviewed the records of 26,000 people from a longstanding national health and nutrition survey to determine prevalence and trends in diabetes. Overall, about 14 percent of the population has diabetes, a third of whom are undiagnosed.

What surprised researchers was their finding that about 21 percent of Asian Americans have diabetes, a prevalence comparable to that in blacks and Hispanics.

“Then to also find that about 50 percent of diabetes is undiagnosed in Asian Americans — it was those two statistics that are scary,” Cowie said.

Data for specific groups within the Asian American population were not available.

The good news is that by learning more about who has diabetes, and who has the disease but doesn’t know it, health officials can better target research and prevention efforts, they said.

"You can intervene. You can increase physical activity, and you can eat a better diet," Cowie said. "You really can reduce your risk."

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