Low, high BMI increased mortality in Asians

**Zheng W. N Engl J Med. 2011;364:719-729.**

A study involving more than 800,000 East Asians has shown that both low and high BMI increased the likelihood of death from any cause, as well as cause-specific death.

However, researchers looked at nearly 300,000 Indians and Bangladeshis and found that only low BMI elevated the risk for death.

The more than 1.14 million participants who comprised the study were recruited in 19 Asian cohorts. Investigators defined 10 BMI levels, ranging from lowest (≤15) to highest (>35) and carried out pooled analyses of individuals to determine the association between BMI (mean 22.9 ± 3.6) and mortality risk.

During a mean follow-up of 9.2 years, approximately 120,700 cohort members died, with CVDs reported as the main cause of death (35.7%), followed by cancer (29.9%). For East Asians, or those from China, Japan or Korea, the lowest risk for death was among those with a BMI between 22.6 and 27.5. The risk was elevated for those with a BMI of 15 or less by a factor of 2.8 and for those with a BMI of more than 35 by a factor of 1.5.

For the cohorts composed of Indians and Bangladeshis, the risk for death from any cause was increased among those with a BMI of 20 or less vs. those with a BMI between 22.6 and 25, but not for those with a higher BMI.

“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,” the researchers concluded. “Given the limitations of the current study, in which the risk of death was used as the outcome, additional studies are needed to quantify the association between BMI and the incidence of disease, in order to better define BMI criteria for overweight and obesity in Asians.” – by Brian Ellis

This is an interesting study. The “obesity paradox“ in Western countries is already known. Although obesity is a risk factor for diabetes, hypertension, CAD and premature death, in the systolic HF (stage C ) population, higher BMI is associated with a better prognosis. Similarly, in patients undergoing CABG, higher BMI is associated with a better prognosis. Cardiac cachexia (increased tumor necrosis factor-alpha) is associated with poor prognosis in systolic HF and in cancer.

Based upon my personal knowledge about Asian Indians, Bangladeshis and Pakistanis, the life expectancy is lower due to a variety of causes in urban people. In rural areas, even though the people are thinner, they live longer. I think lifestyles play an important role in regulating BMI in every country.

– Kanu Chatterjee, MD

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