Underweight Asians Face Higher Risk of Death

A new study of more than 1.1 million people in six Asian countries finds that, like Westerners, Asians are more likely to die if they are overweight or obese. However, some of the highest death rates were seen in people who were severely underweight.

Many previous studies have found that the risk of death increases as body-mass index increases. Body-mass index, or BMI, is a measure of body fat based on height and weight. The trouble is, those studies mostly analyzed Europeans and other Westerners. So scientists couldn't be sure if the results applied to other groups.

To find out, Wei Zheng of Vanderbilt University and his colleagues collected data from China, Taiwan, South Korea, Japan, Bangladesh, and India. Adding up all the numbers, they concluded that the relationship between BMI and death rate in these Asian populations is generally consistent with studies of Westerners.

"Those people with lowest mortality in East Asian countries are those with normal weight," Zheng said. "And then with the reduced BMI and also increased BMI, they have increased risk of death."

That part about those with "reduced BMI" is important because proportionately, more people in Asia are at the lower end of the BMI scale.

"For example, those with BMI less than 15, so this study shows really those with very low BMI have very high risk of death. This is a clear message for those people, [they] need to gain weight."

The study also highlighted a surprising difference between East Asians and South Asians. Among the Indians and Bangladeshis, a higher BMI - in the overweight and obese range - did not translate into a notably higher death rate. Zheng says it might be that their weight reflected prosperity and a higher position in their community.

"They had relatively high socioeconomic status, so they had better access to health care," he suggested.