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