Central obesity measures, including waist circumference and waist-to-hip ratio, showed higher colorectal cancer (CRC) risks compared with body mass index, according to a recent study.

Researchers examined whether colorectal cancer cases attributed to obesity, as measured by BMI, were underestimated compared with central obesity metrics, including waist circumference and waist-to-hip ratio. The analysis utilized data from 458,543 patients aged 40 to 69 years from the UK Biobank cohort, collected between 2006 and 2010, with follow-up extending over a median of 11.8 years.

Published in JAMA Network Open, the study calculated hazard ratios and population attributable fractions for CRC incidence associated with BMI, waist circumference, and waist-to-hip ratio. Anthropometric data were collected during baseline assessments using standardized methods, and cancer diagnoses were identified through national registries. To address potential reverse causation caused by prediagnostic weight loss, the researchers performed sensitivity analyses excluding up to the first 7 years of follow-up.

Key findings demonstrated that hazard ratios for CRC were stronger for central obesity metrics compared with for BMI, noted lead study author Fatemeh Safizadeh, of Heidelberg University in Germany, and colleagues. The hazard ratios for the highest versus lowest quartiles were 1.23 for BMI, 1.37 for waist circumference, and 1.4 for waist-to-hop ratio. Excluding the initial 7 years of follow-up, the hazard ratio for BMI increased to 1.37, aligning more closely with central obesity measures. These adjustments accounted for potential biases linked to cancer-related cachexia.

The population attributable fractions for CRC also varied by obesity metric. For the full follow-up period, they were 9.9% for BMI, 17.3% for waist circumference, and 17.6% for waist-to-hip ratio. After excluding the first 7 years, population attributable fractions increased to 15.7% for BMI, 16.9% for waist circumference, and 18% for waist-to-hip ratio.

The researchers concluded that central obesity measures more comprehensively reflect CRC risk attributable to excess weight. These findings highlight the importance of incorporating waist circumference and waist-to-hip ratio into clinical and public health approaches to CRC prevention, as reliance on BMI alone may underestimate the obesity-related burden of CRC.

Full disclosures can be found in the published study.