The association between BMI and the risk of death in Asia is mostly similar to that seen in people of European origin, but there may be some important differences between populations, suggesting that underweight may be a more potent risk factor than overweight in Asia. In a large pooled analysis including more than 1.1 million people in 19 separate Asian cohorts, Wei Zheng and colleagues found a U-shaped curve among East Asians in which the lowest risk of death was found in people with a BMI in the range of 22.6 to 27.5. Risk was elevated by as much as 1.5 times in East Asians with a BMI over 35 and by as much as 2.8 times in those with a BMI of 15 or lower.

However, among Indians and Bangladeshis high BMI was not associated with an excess risk of death, although the association with low BMI remained significant. In the discussion section of their report in the New England Journal of Medicine, the authors note that “socioeconomic status could confound the association between BMI and the risk of death, since in less well-developed countries, people with a high BMI are more likely to have a high socioeconomic status (and thus better access to health care) than are those with a lower BMI.”

The authors concluded that “overall, the risk of death among Asians, as compared with Europeans, seems to be more strongly affected by a low BMI than by a high BMI.”