Estimates of the relative mortality risks associated with normal weight, overweight, and obesity may help to inform decision making in the clinical setting.
To 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.
PubMed and EMBASE electronic databases were searched through September 30, 2012, without language restrictions.
Articles 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 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).
Random-effects summary all-cause mortality HRs for overweight (BMI of 25-<30), obesity (BMI of ≥30), grade 1 obesity (BMI of 30-<35), and grades 2 and 3 obesity (BMI of ≥35) were calculated relative to normal weight (BMI of 18.5-<25). The summary HRs were 0.94 (95% CI, 0.91-0.96) for overweight, 1.18 (95% CI, 1.12-1.25) for obesity (all grades combined), 0.95 (95% CI, 0.88-1.01) for grade 1 obesity, and 1.29 (95% CI, 1.18-1.41) for grades 2 and 3 obesity. These findings persisted when limited to studies with measured weight and height that were considered to be adequately adjusted. The HRs tended to be higher when weight and height were self-reported rather than measured.
结果显示，超重（BMI25—30）、肥胖症（BMI ≥30）、1级肥胖（BMI為30—35）、2级和3级肥胖（BMI≥35）的全因死亡率风险比的计算（HR）是相较于正常体重（BMI为18.5—25）的。风险比分析结果表明，超重的死亡风险为0.94 (95%置信区间为0.91—0.96)；肥胖（全部分级总和）的死亡风险为1.18 (95% 置信区间为1.12—1.25)；1级肥胖的死亡风险为0.95 (95% 置信区间为0.88—1.01)；而2级和3级肥胖的死亡风险为1.29 (95% 置信区间为1.18—1.41)。这些发现仅与那些测量了患者体重、身高并进行了合适校正的研究相一致。与测量患者体重、身高指标的研究相比，自报体重、身高指标的研究的风险比更高。
and Relevance Relative to normal weight, both obesity (all grades) 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.