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Waist measurement, not BMI, is stronger predictor of death risk, study finds

BMJ 2017; 357 doi: https://doi.org/10.1136/bmj.j2033 (Published 26 April 2017) Cite this as: BMJ 2017;357:j2033
  1. Jacqui Wise
  1. London

People with a normal body mass index (BMI) but a large waist circumference have worse long term survival than people who are overweight or obese but who do not carry their weight around the middle, a study has found. The finding, published in Annals of Internal Medicine,1 is consistent with previous research but is from a much larger sample of adults in the general population.

The study included 42 702 participants from 10 years of the Health Survey for England and the Scottish Health Survey. Participants’ mean age was 57.7, and 46.8% were men. The researchers found that 43.7% of participants were overweight (BMI 25 to <30) and 25% were obese (BMI ≥30).

The overall prevalence of central obesity was 53.4%—defined as a waist to hip ratio of 0.85 or higher in women and 0.90 in men. The prevalence of central obesity among normal weight, overweight, and obese participants was 28.7%, 60.2%, and 72.7%, respectively.

A total of 5355 people died over 383 542 person years of follow-up. The researchers found that, when compared with the normal weight participants without central obesity, only normal weight and obese people with central obesity were at increased risk for all cause mortality. Compared with overweight participants without central obesity, their counterparts with central obesity were at increased risk for mortality (hazard ratio 1.11 (95% confidence interval 1.01 to 1.23)). Obese participants with central obesity were also at higher risk for mortality than their counterparts without central obesity (1.27 (1.09 to 1.47)).

A total of 1720 participants died of cardiovascular disease. Compared with normal weight participants without central obesity, all participants with central obesity were at increased risk for death from cardiovascular disease. The results were similar when men and women were analysed separately.

The researchers, from Loughborough University, said, “Explaining these paradoxical findings in overweight and obese persons, even in the presence of central obesity, is challenging. One possibility is that overweight and obese persons have greater amounts of subcutaneous fat in the hips and legs—that is, fat linked to healthier metabolic profiles.”

However, they noted that that the study relied on a single clinical assessment and that weight histories might have been more informative.

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