Standard BMI cutoff for obesity ‘may not be appropriate’ in Asian Americans

There is substantial heterogeneity in obesity prevalence among subgroups of Asian American adults, according to a recent study published in Annals of Internal Medicine.

Researchers said the findings suggest that the burden of obesity and related cardiometabolic effects “may be underrecognized without studying each Asian American subgroup individually.”

Despite being the fastest growing racial group in the United States, Nilay S. Shah, MD, MPH, an assistant professor of medicine and preventive medicine at Northwestern Medicine, and colleagues said that Asian Americans continue to be “underrepresented and are frequently inadequately characterized in data on health status and outcomes.”

Grouping all Asian Americans into a sole “Asian” category exacerbates this issue, the researchers said, which hides important heterogeneity data that would be available if the subgroups were categorized as their own.

“Such aggregation may underestimate or overestimate health status and chronic disease complications among certain Asian American subgroups,” they wrote.

Population data, they added, suggest that persons of Asian ancestry may develop adverse health conditions and outcomes at a lower BMI than other ethnic and racial groups.

To characterize obesity prevalence, Shah and colleagues analyzed data that were collected from the Behavioral Risk Factor Surveillance System (BRFSS), a telephone health survey, from 2013 to 2020.

BRFSS participants were divided into three categories of race and ethnicity based on self-identification: non-Hispanic Asian (n = 71,057), non-Hispanic Black (n = 263,136) and non-Hispanic white (n = 2,547,965).

Asian participants were then further divided into several subgroups: Asian Indian (n = 13,916), Chinese (n = 11,686), Filipino (n = 11,815), Japanese (n = 12,473), Vietnamese (n = 2,618) and Korean (n = 3,364).

When using the standard BMI categorization of obesity (equal to or greater than 30 kg/m²), Shah and colleagues found that the overall adjusted obesity prevalence was 11.7% (95% CI, 11.2-12.2) among Asian participants; 39.7% (95% CI, 39.4-40.1) among Black participants; and 29.4% (95% CI, 29.3-29.5) among white participants.

In Asian subgroups, obesity prevalence was highest among Filipino Americans at 16.8% (95% CI, 15.2-18.5) and lowest among Vietnamese Americans at 6.3% (95% CI, 5.1-7.8). Among other subgroups, the prevalence was 15.3% (95% CI, 13.2-17.5) in Japanese Americans; 11.2% (95% CI, 10.2-12.2) in Asian Indian Americans; 8.5% (95% CI, 6.8-10.5) in Korean Americans; and 6.5% (95% CI, 5.5-7.5) in Chinese Americans.

When using a modified threshold for Asian populations — a BMI categorization of 27 kg/m² or greater — the researchers reported that obesity prevalence among Asian participants was 22.4% (95% CI, 21.8-23.1), with Filipino Americans again having the highest prevalence at 28.7% (95% CI, 26.8-30.7). The prevalence among other subgroups was 26.7% (95% CI, 24.1-29.5) in Japanese Americans; 22.4% (95% CI, 21.1-23.7) in Asian Indian Americans; 17.4% (95% CI, 15.2-19.8) in Korean Americans; 13.6% (95% CI, 11.7-15.9) in Vietnamese Americans; and 13.2% (95% CI, 12-14.5) in Chinese Americans.

Based on the results, Shah and colleagues wrote that the ranging heterogeneity of obesity prevalence between Asian American subgroups “was masked by the prevalence estimate in a combined [Asian] group (12%).”

“Clinicians must be aware that the cardiovascular and metabolic risks related to obesity may be different among individuals who belong to different Asian subgroups,” Shah said in a press release. “The standard approach and definitions of obesity based on specific body mass index thresholds may not be appropriate for the Asian American population.”

The researchers also acknowledged that BMI categories may not characterize obesity-related morbidity and mortality risks in adults, and said that study results, combined with prior research, “suggest that a BMI threshold of 25 kg/m² may be inappropriate for defining overweight or obesity or for clinical screening for comorbidities among Asian American adults and adults of other race and ethnic groups.”

Limitations to the study include self-reported data on weight and height — thus susceptible to social desirability and recalls — BRFSS data not being weighted to reflect Asian subgroups and a lack of information on factors such as immigration and time spent in the U.S., according to the researchers.

Despite these limitations, Shah and colleagues concluded that the results may help to not only inform clinicians of potential health risks linked to obesity in Asian American patients, but also to “support efforts by public health professionals to adapt and tailor programs for obesity prevention and management to specific populations that are disproportionately affected.”

In a related editorial, Christina C. Wee, MD, MPH, senior deputy editor of Annals of Internal Medicine, wrote that the findings “remind us that one size does not fit all.”

In recent years, the American Diabetes Association and U.S. Preventive Services Task Force have recommended that providers consider screening Asian Americans for diabetes at a lower BMI than white individuals, according to Wee.

“For obesity management, however, public health and clinical guidelines in the United States provide little guidance specific to Asian American populations,” she wrote. “Because clinicians and payers look to guidelines to guide practice and reimbursement for weight loss interventions, the lack of recommendations specific to patients of Asian descent puts them at risk for delayed treatment.”

References:

• Asian Americans’ obesity prevalence is not one-size-fits-all. https://www.eurekalert.org/news-releases/966762. Published Oct. 4, 2022. Accessed Oct. 4, 2022.
• Shah N, et al. Ann Intern Med. 2022;doi:10.7326/M22-0609.
• Wee CC. Ann Intern Med. 2022;doi:10.7326/M22-2624.