Invited commentary: Body mass index and mortality

Abstract

In the midst of an epidemic of obesity, epidemiologists are seeking to establish the relationship of body mass index (BMI; weight (kg)/height (m) 2) with mortality. In an accompanying article, Adams et al. (Am J Epidemiol. 2014;179(2):135-144) used a subsample of the National Institutes of Health-AARP Diet and Health Study cohort, recruited in 1995-1996 (109,947 people), to examine associations of BMI in early (18 years) and middle (35 and 50 years) adulthood with mortality, as well as the effect of weight gain between these ages on subsequent mortality during 12.5 years' follow-up. They report a positive association between BMI and mortality at each age (using BMI 18.5-22.4 as the referent). Furthermore, there were strong positive associations of weight gain between ages 18 and 35 years and ages 35 and 50 years with mortality. Attainment of a BMI of 25 or higher at a younger age increased risk of death. The findings contrast sharply with those of a recent systematic review and meta-analysis of 97 studies, which found that only the grade 2 and 3 obesity categories (i.e., BMI ≥ 35) were responsible for elevated risk of mortality, with slight protection from overweight (25.0-29.9). Due consideration of the limitations of BMI as a measure of detrimental adiposity and of mortality measures alone to inform clinical practice is indicated. © The Author 2013. Published by Oxford University Press on behalf of the Johns Hopkins Bloomberg School of Public Health. All rights reserved.