Research News

Overweight people live longest

BMJ 2013; 346 doi: http://dx.doi.org/10.1136/bmj.f75 (Published 09 January 2013) Cite this as: BMJ 2013;346:f75

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Although a body mass index (BMI) of 18.5 to <25 is considered normal, all cause mortality is lowest among people with a BMI of 25 to <30, who are termed overweight, according to a systematic review. The review identified 143 papers, and, after eliminating overlap, 97 studies comprising 2.88 million people were pooled in a meta-analysis.

Compared with normal BMI, hazard ratios for all cause mortality were 0.94 (95% CI 0.91 to 0.96) for overweight, 1.18 (1.12 to 1.25) for obesity overall (BMI ≥30), 0.95 (0.88 to 1.01) for grade 1 obesity (BMI 30 to <35), and 1.29 (1.18 to 1.41) for grades 2 and 3 obesity (BMI ≥35). Researchers examined the role of various confounders and biases, and the results were consistent across analyses.

It could be that risk factors are better managed in overweight and obese people, but we also know that BMI and mortality are inversely related in the presence of a wasting disease, heart or kidney disease, diabetes, and old age (editorial, p 87). The results could also be an artefact; in most studies, the lowest all cause mortality was seen in patients with a BMI of 22-25, but the “normal” range also includes people with a BMI of 18.5-22 who have a higher mortality.

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Cite this as: BMJ 2013;346:f75