Obesity in Asian American Subgroups Varies, Starts at Lower BMI

Marlene Busko

October 03, 2022

Obesity and the associated increased risk for cardiometabolic disease is missed in Asian Americans when using the standard body mass index (BMI) cutoff for obesity rather than a suggested lower threshold for obesity in Asians, new research in an American Asian population showed.

Moreover, the study showed that the six largest subgroups of Asian Americans — Asian Indian, Japanese, Filipino, Chinese, Korean, and Vietnamese Americans, in descending order of size — differ greatly in their rates of obesity.

In 2004, the World Health Organization (WHO) suggested that instead of defining obesity as a BMI ≥ 30 kg/m2, a lower threshold of a BMI ≥ 27.5 kg/m2 should be used to define obesity in Asians.

Using data from the Behavioral Risk Factor Surveillance System (BRFSS) surveys, and the standard definition of obesity, the researchers estimated that overall, the prevalence of obesity was 11.7% in Asian Americans — ranging from 6.3% to 16.8% in different subgroups.

However, using the lower cutoff for obesity, the prevalence essentially doubled to 22.4% overall, and obesity rates in Filipino and Japanese Americans were 28.7% and 26.7%, respectively, close to the 29.4% rate of obesity in White people in this sample, although less than the 39.7% rate of obesity in Black individuals in this sample.

The study by Nilay S. Shah, MD, MPH, and colleagues was published online today in the Annals of Internal Medicine.

"Wide Differences" in Obesity Prevalence Among Asian Americans

The main finding of this work is that the number of Asian Americans with obesity, "a fundamental risk factor for several chronic diseases," is much higher using the definition for Asians, Shah, assistant professor of medicine (Cardiology) and preventive medicine, Northwestern University Feinberg School of Medicine, Chicago, explained in an interview with Medscape Medical News.  

Second, the study showed that there are "really wide differences in the prevalence of obesity" in Asian Americans, he noted.

"In addition to our data, other work that is being done in this space is strong enough to at least recommend to clinicians that they should be considering obesity-related risks at lower BMI in Asian American populations," he said.

"For the longest time, individuals who identified as Asian were grouped into one category," Shah continued. However, in the last 5 to 10 years, "we really started to understand that the communities that make up the Asian American population are actually very diverse in things like health behaviors, socioeconomic patterns, educational attainment, and English language literacy," which contribute to health.

"Asian Americans have been the fastest growing racial or ethnic population in the US for the last decade and projected to be the fastest growing over the next 30 years," he noted.

Future research should continue to characterize differences in obesity and cardiovascular risk factors in individual Asian American subgroups, the researchers conclude.

Unrecognized Obesity, Risk of Delayed Treatment in Asian Subgroups

Writing in an accompanying editorial, Christina C. Wee, MD, MPH, notes that "obesity is among the leading causes of preventable deaths, a focus of research, and a public health priority in the United States and worldwide."

However, "the United States has paid insufficient attention to the problem of obesity in Asian Americans, the country's most rapidly growing ethnic group, in part because of the perception that they are at low risk for obesity and its  adverse health effects," said Wee, senior deputy editor, Annals of Internal Medicine, and vice president, Annals Division of the American College of Physicians.

Until the past decade, the US did not consistently track the prevalence of overweight and obesity in Asian Americans.

The study by Shah and colleagues is "one of the first times we have looked at prevention in [Asian] subgroups," and it highlights two issues, she told Medscape Medical News: how to define obesity in Asians, and that not all Asian Americans are the same even with the modified definition.

The rate of obesity in Chinese Americans is still low, whereas it is quite high in Filipino and Japanese Americans.

Despite the WHO's 2004 report, the adoption of a lower BMI threshold to classify risk for Asian Americans has been slow in the United States, Wee wrote, and not surprisingly, a 2017 study found that Asian Americans were three times more likely than Whites to have undiagnosed diabetes.

Although new guidelines recommend screening earlier for diabetes in Asians, "for obesity management, however, public health and clinical guidelines in the United States provide little guidance specific to Asian American populations," Wee notes. 

"Because clinicians and payers look to guidelines to guide practice and reimbursement for weight loss interventions," Wee adds, " the lack of recommendations specific to patients of Asian descent puts them at risk for delayed treatment." 

"Many decades into our 'war against obesity,' Shah and colleagues remind us that one size does not fit all," she concludes.

Higher Obesity in Asian Indian, Japanese, and Filipino Americans

The researchers aimed to determine the degree of variation in obesity in Asian Americans, using both the standard definition of obesity and the definition for Asians.

Using BRFSS data from 2013-2020, the researchers identified 2.8 million adults aged 18 years and older, including 2.5 million non-Hispanic White persons, 263,136 Black individuals, and 71,057 non-Hispanic Asian people (comprised of 13,916 Asian Indians, 11,686 Chinese, 11,815 Filipino, 12,473 Japanese, 3634 Korean, and 2618 Vietnamese Americans).  

The prevalence of obesity among Vietnamese, Chinese, and Korean Americans was 6.3%, 6.5%, and 8.5%, respectively, using the standard definition, but it was 13.6%, 13.2%, and 17.4%, using the suggested definition for Asians.

The prevalence of obesity was highest among Asian Indian, Japanese, and Filipino Americans: 11.2%,15.3%, and 16.8%, respectively, using the standard definition, and it was 22.4%, 26.7%, and 28.7%, using the lower BMI cutoff.

The researchers acknowledge that a study limitation is that the BMI was based on self-reported height and weight, but this would tend to underestimate the true prevalence they note.

"Substantial heterogeneity in obesity prevalence exists among Asian American subgroups in the United States. Future studies and public health efforts should consider this heterogeneity," they conclude. 

The study was funded by a grant from the National Heart, Lung, and Blood Institute. Shah and Wee report no relevant financial relationships.

Ann Intern Med. Published online October 3, 2022. Abstract, Editorial

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