Studies show that at a normal body weight — generally considered a body mass index, or B.M.I., below 25 — people of any Asian ancestry, including those who are Chinese, Filipino and Japanese, have a greater likelihood of carrying this dangerous type of fat. Despite having lower obesity rates than whites, Asian-Americans have twice the prevalence of Type 2 diabetes, which promotes heart attacks and strokes.

Heart risks tended to be greatest in South Asians, the Masala researchers found. In one recent study, in the Annals of Internal Medicine, they found that 44 percent of the normal weight South Asians they examined had two or more metabolic abnormalities, like high blood sugar, high triglycerides, hypertension or low HDL cholesterol, compared to just 21 percent of whites who were normal weight.

The Masala researchers also found that using the standard cutoff point to screen for diabetes, a B.M.I. of 25 or greater, would cause doctors to overlook up to a third of South Asians who have the disease. “Many of them may never get to that B.M.I. and they will have had diabetes for years,” Dr. Kanaya said.

The findings helped prompt the American Diabetes Association to issue updated guidelines in 2015 that lowered their screening threshold for diabetes, to a B.M.I. of 23 for Asian-Americans. A public awareness campaign, organized by the National Council of Asian Pacific Islander Physicians, called Screen at 23 has drawn attention to the issue, and a.t least three states, including California, Massachusetts and Hawaii, have enacted policies to promote more aggressive health screenings of Asian-Americans. Representative Pramila Jayapal of Washington, the first Indian-American woman to serve in the House, recently introduced a bill to provide more funding for South Asian heart health awareness and research.

Most of the participants in the Masala study are first-generation immigrants, and the researchers found that their cultural practices also impact their disease rates. Cardiovascular risks tended to be highest in two groups: those who maintained very strong ties to traditional South Asian religious, cultural and dietary customs, and those who vigorously — embraced a Western lifestyle. Those with lower risk are what the researchers call bicultural, maintaining some aspects of traditional South Asian culture while also adopting some healthy Western habits.

This discrepancy plays out in their dietary behaviors. Almost 40 percent of Masala participants are vegetarian, a common practice in India that is widely regarded in the West as heart healthy. But vegetarians who eat traditional South Asian foods like fried snacks, sweetened beverages and high-fat dairy products were found to have worse cardiovascular health than those who eat what the researchers call a “prudent” diet with more fruits, vegetables, nuts, beans and whole grains (and, for nonvegetarians, fish and chicken). People who eat a Western style diet with red and processed meat, alcohol, refined carbohydrates and few fruits and vegetables were also found to have more metabolic risk factors.

Dr. Namratha Kandula, a Masala investigator at Northwestern, said she hopes to study the children of the Masala participants next because they tend to influence their parents’ health and lifestyle habits, and the researchers want to understand whether health risks in second-generation South Asians are similar or not. But for now, some experts say their goal is to increase outreach to South Asians who may be at high risk and neglecting their health.

“As a South Asian Bay Area resident, I see that we focus a lot on success and academic achievements in our families,” said Dr. Khandelwal at Stanford. “But we don’t necessarily look at our health success, and your health is something that you can’t easily get back.”