Association between Mortality and Obesity

Posted On 2013-01-07 13:55:53
In a recent article published in JAMA, the authors describe results from a systematic review of reported hazard ratios (HRs) of all causemortality for overweight  and obesity relative to normal weight in the general population (1). PubMed and EMBASE electronic databases were searched through September 30, 2012. 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. 97 studies were retained for analysis, providing a combined sample size of more than 2.88 million individuals and more than 270,000 deaths.

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. 

Relative to normal weight, both obesity (all grades) and grades 2 and 3 obesity were associated with significantly higher all-cause mortality. However, grade 1 obesity overall was not associated with higher mortality, and overweight was associated with significantly lower all-cause mortality. 

In an accompanying editorial the authors discuss that this question has engaged the interest of the public, health care professionals, and a wide range of clinical investigators and has profound health, social, and economic implications for individuals, communities, and the population as a whole. (2)

1. Association of all-cause mortality with overweight and obesity using standard body mass index categories: a systematic review and meta-analysis.Flegal KM, Kit BK, Orpana H, Graubard BI. JAMA. 2013;309:71-82. 

2. Heymsfield SB, Cefalu WT. Does body mass index adequately convey a patient's mortality risk? JAMA. 2013;309:87-8. doi: 10.1001/jama.2012.185445.