JAMA

ImportanceEstimates of the relative mortality risks associated with normal weight, overweight, and obesity may help to inform decision making in the clinical setting.ObjectiveTo perform a systematic review of reported hazard ratios (HRs) of all-cause mortality for overweight and obesity relative to normal weight in the general population.Data SourcesPubMed and EMBASE electronic databases were searched through September 30, 2012, without language restrictions.Study SelectionArticles that reported HRs for all-cause mortality using standard body mass index (BMI) categories from prospective studies of general populations of adults were selected by consensus among multiple reviewers. Studies were excluded that used nonstandard categories or that were limited to adolescents or to those with specific medical conditions or to those undergoing specific procedures. PubMed searches yielded 7034 articles, of which 141 (2.0%) were eligible. An EMBASE search yielded 2 additional articles. After eliminating overlap, 97 studies were retained for analysis, providing a combined sample size of more than 2.88 million individuals and more than 270 000 deaths.Data ExtractionData were extracted by 1 reviewer and then reviewed by 3 independent reviewers. We selected the most complex model available for the full sample and used a variety of sensitivity analyses to address issues of possible overadjustment (adjusted for factors in causal pathway) or underadjustment (not adjusted for at least age, sex, and smoking).ResultsRandom-effects summary all-cause mortality HRs for overweight (BMI of 25\ue2\u20ac\u201c<30), obesity (BMI of \ue2\u2030\ua530), grade 1 obesity (BMI of 30\ue2\u20ac\u201c<35), and grades 2 and 3 obesity (BMI of \ue2\u2030\ua535) were calculated relative to normal weight (BMI of 18.5\ue2\u20ac\u201c