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Mortality rises with waist size

Larger waists raise all-cause mortality independently of BMI

Louise Prime

Wednesday, 11 August 2010

New research showing that all-cause mortality is greatest in people with large waists could mean a revision of guidelines on obesity management is needed, say authors in the current Archives of Internal Medicine.

Previous research had already shown associations between a large waist – which correlates closely with visceral fat – and inflammation, insulin resistance, type 2 diabetes, abnormal cholesterol levels and heart disease. These US researchers set out to measure the effect on mortality of increasing waist circumference.

Demographic, medical and behavioural data had been recorded in 1992/3 for 48,500 men and 56, 343 women, all aged at least 50 years, taking part in the Cancer Prevention Study II Nutrition Cohort. Participants had also supplied information about their weight and waist measurement in 1997. During the following nine years, up to the end of 2006, 9315 participating men and 5332 women died.

Researchers looked for an association between waist circumference and risk of death. After they had adjusted for body mass index (BMI) and other known risk factors, having a very large waist (at least 120cm/47” for men and at least 110cm/42” for women) more than doubled the risk of death during the study period compared with having a waist less than 90cm for men and 75cm for women.

Whether people were of normal weight, overweight or obese, having a larger waist increased mortality. For women, the association was strongest for women of a normal weight.

The authors say: “The reason for the stronger association between waist circumference and mortality among women with low BMI in our study is unclear. Future detailed analyses of the relationship between waist circumference and visceral adipose tissue or measures of insulin resistance within categories of BMI could identify biological reasons for potential differences in the strength of the association between waist circumference and mortality.”

The researchers suggest that their findings could influence future obesity guidelines: “Currently available clinical guidelines from the National Institutes of Health are based on evidence from the 1990s. These guidelines recommend that waist circumference be used to identify increased disease risk only among individuals in the overweight and obese categories of BMI.

“In addition, the NIH guidelines recommend weight loss goals for all patients in the obese category of BMI (30 or greater), but they do not specifically recommend weight loss goals for abdominally obese patients (waist circumference of 88cm or larger in women or 102cm or larger in men) who are in the normal or overweight BMI category unless they also have two or more cardiovascular risk factors or a desire to lose weight.”

Arch Intern Med. 2010;170[15]:1293-1301

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