Any Amount of Excess Body Weight Associated With Higher Risk of Premature Death Interview with:

Dr. Shilpa Bhupathiraju, PhD Harvard T.H. Chan School of Public Health

Dr. Shilpa Bhupathiraju

Dr. Shilpa Bhupathiraju, PhD
Harvard T.H. Chan
School of Public Health What is the background for this study? What are the main findings?

Response: We wanted to investigate the association between body mass index (BMI) and mortality across major global regions. In doing so, we wanted to take into account important methodological limitations which plagued prior reports of BMI and mortality. One such limitation is reverse causality where a low body weight is the result of an underlying illness rather than the cause. Another major problem is confounding due to smoking where smokers have lower body weights than non-smokers but have much higher mortality rates.

Therefore, to obtain an unbiased association between BMI and mortality, our primary pre-specified analysis was restricted to never smokers and those who had no existing chronic diseases at the start of the study.

In this group, we found that those with a BMI of 22.5-<25 kg/m2 (considered a healthy weight range) had the lowest mortality risk during the time they were followed. The risk of mortality increased significantly with excess body weight. A BMI of 25-<27.5 kg/m2 (in the overweight range) was associated with a 7% higher risk of premature death; BMI of 27.5-<30 kg/m2 (also in the overweight range) was associated with a 20% higher risk; a BMI of 30.0-<35.0 kg/m2 was associated with a 45% higher risk; a BMI of 35.0-<40.0 kg/m2 was associated with a 94% higher risk; and a BMI of 40.0-<60.0 kg/m2 was associated with a nearly 3-fold risk. In general, we found that the association of excess body weight with mortality was greater in younger than older people and in men than women. Most importantly, the associations were broadly consistent in the major global regions we examined, including Europe, North America, Australia and New Zealand, East Asia, and South Asia. What should readers take away from your report?

Response: It is important for the readers to understand that any amount of excess body weight is associated with a higher risk of premature death, including deaths from cardiovascular disease, cancer, and respiratory disease. At the same time, doctors need to continue to counsel their patients regarding the deleterious effects of excess body weight which include a higher risk of diabetes, cardiovascular disease, and cancer. What recommendations do you have for future research as a result of this study?

Response: Future studies should look at different measures of adiposity and different aspects of body composition such as visceral fat or fat distribution. Further, South Asian cohorts were underrepresented in our study. Because South Asians have a higher amount of body fat for a given BMI compared to their European counterparts, large studies in this region will shed more light on the BMI-mortality relationship in this group. Finally, as we had no data from Latin America and Africa, future studies should examine the BMI-mortality association in these populations. Is there anything else you would like to add?

Response: Our study is the largest and most rigorous effort to resolve the controversy regarding BMI and mortality. Contrary to prior reports of an “obesity-paradox”, we found that once we take into account serious methodological limitations (such as reverse causation and confounding that can invalidate findings), excess body weight is associated with a higher risk of premature death. Strategies to combat excess adiposity worldwide should start early on in life. Thank you for your contribution to the community.


Body-mass index and all-cause mortality: individual-participant-data meta-analysis of 239 prospective studies in four continents

The Lancet , Volume 0 , Issue 0
Published Online: 13 July 2016

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Last Updated on July 15, 2016 by Marie Benz MD FAAD