Retrospective cohort study of the association of central obesity with the risk of colorectal cancer

The proportion of colorectal cancer (CRC) cases attributable to excess weight, known as population attributable fraction (PAF), has been commonly based on measures of body mass index (BMI). Central obesity metrics, such as waist circumference (WC) and waist to hip ratio (WHR) are potentially better indicators of adiposity. A retrospective cohort study using the UK Biobank included 458,543 participants. The proportions of CRC cases attributable to high WC and to high WHR were 17.3% and 17.6%, respectively. These estimates were substantially higher compared with the corresponding estimate for high body mass index (9.9%), which increased to 15.7% when bias due to prediagnostic weight loss was addressed. These associations were observed in the overall cohort and in subgroups. The authors conclude that these findings suggest that central obesity metrics are likely to more comprehensively reflect the proportion of CRC cases attributable to obesity.