People of Hispanic, African-American, and Asian descent could be at high risk for factors related to heart disease even if they are not overweight or obese, according to the lead author of a new study.
The research, published this week in the Annals of Internal Medicine, found that among people of normal weight, South Asians were twice as likely as whites to have risk factors for heart disease.
That likelihood was 80 percent greater for Hispanics and 50 percent for blacks and people of Chinese descent, the research found.
"One of the messages of the paper is that in using overweight and obesity as the main criteria, clinicians are likely to miss a large number of people, especially in race-ethnic minority populations, that are at high risk but are normal weight," Unjali Gujral, a postdoctoral fellow with the Emory Global Diabetes Research Center and the study's lead author, told NBC News by phone Tuesday.
Body mass index (BMI), a height-to-weight ratio, is used to determine whether someone is overweight or obese. The U.S. Preventive Services Task Force, an independent group of health experts, recommends that doctors use this ratio as the main criteria to screen for risk factors associated with heart disease and diabetes, according to the study.
Those factors include low HDL (often called good cholesterol); elevated triglycerides (fat found in blood); elevated glucose (blood sugar); and high blood pressure, the study said.
The presence of at least two translates to a higher risk of having heart disease, diabetes, or stroke.
But a BMI number by itself may not be a one-size-fits-all standard for deciding whether to check for heart disease risks, the study suggests.
The World Health Organization (WHO) defines normal BMI as 18.5 to 24.9; overweight as 25.0 to 29.9; and obese as 30 and over.
The ranges differ slightly for South Asians and Chinese, two groups where heart disease and diabetes are known to occur at lower BMIs. For them, normal runs from 18.5 to 22.9; overweight from 23.0 to 27.4; and obese, 27.5 and higher.
The study estimated the necessary BMI for each race and ethnic group that would be equal to the same number of heart health risk factors as someone who is white with a 25.0 BMI, the low end of overweight, Gujral said.
For people of color, those BMI results came out lower: 22.9 for blacks, 21.5 for Hispanics, 20.9 for Chinese, and 19.6 for South Asians, the study found.
All of them were considered normal weight on the BMI scales.
"In short, what that tells us is that a person of a race-ethnic minority group could be thinner than a white individual and still have the same amount of heart health risk factors," Gujral said.
The researchers culled data on 7,617 people taken from two separate studies. Among them were 803 Chinese Americans and 803 South Asians, who represented countries including India, Pakistan, Nepal, Bangladesh, and Sri Lanka.
It also included 2,622 whites, 1,893 blacks, and 1,496 Hispanics. Gujral said the age of participants began at 45.
The study was conducted by Emory University in Atlanta and the University of California, San Francisco.
One limitation, Gujral said, was that researchers couldn't say for sure whether the findings would be exactly the same for other East Asian ethnicities like Koreans or Japanese. Gujral said there is a shortage of studies with data on Asian Americans.
"But we can speculate we would have a higher risk in all Asian populations for these heart disease risk factors at normal weight compared to white individuals," she added.
Gujral also said results may vary for South Asians born in the United States. Those in the study were immigrants, she said.
Participants were also older, Gujral noted, meaning that the findings could be somewhat different for younger populations.
In all groups, Gujral said, certain factors like education, age, and where fat is stored in the body explained why someone would be at normal weight yet still have a high risk of cardiovascular disease.
"What these factors didn't explain were the differences in this high cardiometabolic risk in normal weight people across ethnic groups," she added.
Gujral said she hopes the study sparks dialogue between patients and doctors, so that people of color with normal weight get screened for factors considered risks for heart disease, diabetes, and stroke.
"The major takeaway would be just for individuals who are members of race-ethnic minority populations to be aware of this increased risk and to have conversations with physicians or healthcare providers about their increased risk," she said.