Databyte: Long Live the Overweight?

A closer look at the results of a recent meta-analysis in JAMA

Published on January 29, 2013 by Dana March


Recently, we featured an analysis of the controversy shrouding a systematic review and meta-analysis published in JAMA on New Year’s Day. The review rigorously examined the link between BMI-based weight categories and risk of death from all causes. The most incendiary finding of the study was that overweight people seem to live about six percent longer than normal weight people.

In the article, the study results were strikingly visually arrayed as curvy spines, with each of the constituent studies as vertebrae. This adaptation of a figure (left) presents data comparing risk of death in those who are overweight to those who are normal weight, using BMI measures that were collected by the researchers themselves. The blue vertebrae represent studies that found being overweight was linked to longer life spans (hazard ratio less than 1). The two pink vertebrae represent studies that found no difference in length of life (hazard ratio equals 1), and the red vertebrae represent studies that found being overweight was linked to shorter life spans (hazard ratio greater than 1). The dashed lines represent those studies that were not statistically significant (the confidence intervals were in the longer life area and the shorter life area). While the scoliotic map of scientific evidence showed a wide range of individual study results, far more studies found that being overweight was associated with a longer life. The reverse was true for the obesity-normal BMI comparison (not pictured). For the overweight, but not obese, it appears this study has their backs.

Dana March
Dana March, Editor-in-Chief of the2x2project, is an Assistant Professor in the Department of Epidemiology at Columbia’s Mailman School of Public Health. Her research addresses the ways in which our social lives and where we live shape population health and how we respond to interventions. She has particular interests in urbanization and the social fault lines of health, like race and class. March has written for Newsweek and her work has been featured in Scientific American. She is a 2014-15 Public Voices Fellow at Columbia University Medical Center. Follow her on Twitter @Dana_March. Email her at

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1 Comment

Did the study adequately control for the effects of wasting, i.e. pronounced weight loss that often occurs with advanced chronic illness, like cancer, and often precipitates death? If not, it would give the appearance that being underweight is associated with mortality, and the researchers might have interepreted this as causal.

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