Estimates of the relative mortality risks associated with normal weight, overweight, and obesity may help to inform decision making in the clinical setting.
Dr Katherine Flegal and colleagues performed a systematic review of reported hazard ratios of all-cause mortality for overweight and obesity relative to normal weight in the general population.
The team searched PubMed and EMBASE electronic databases through 2012, without language restrictions.
The researchers identified articles that reported hazard ratios for all-cause mortality using standard body mass index categories from prospective studies of general populations of adults.
The studies 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.
The researchers found that PubMed searches yielded 7034 articles, of which 141 were eligible.
An EMBASE search yielded 2 additional articles.
|The summary hazard ratio was 1.18 for obesity|
|Journal of the American Medical Association|
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 was extracted by 1 reviewer, and then reviewed by 3 independent reviewers.
the team selected the most complex model available for the full sample, and used a variety of sensitivity analyses to address issues of possible overadjustment or underadjustment.
The research team found that the summary hazard ratios were 0.94 for overweight, 1.18 for obesity, 0.95 for grade 1 obesity, and 1.29 for grades 2 and 3 obesity.
The doctors noted that these findings persisted when limited to studies with measured weight and height that were considered to be adequately adjusted.
The hazard ratios tended to be higher when weight and height were self-reported rather than measured.
Dr Flegal and team concludes, "Relative to normal weight, both obesity, and grades 2 and 3 obesity were associated with significantly higher all-cause mortality."
"Grade 1 obesity overall was not associated with higher mortality, and overweight was associated with significantly lower all-cause mortality."
"The use of predefined standard BMI groupings can facilitate between-study comparisons."