Percent Body Fat Measured by Bioelectrical Impedance is Not Associated with Colorectal Adenoma Status.

Background: Obesity is a risk factor for colorectal neoplasia. Bioelectrical impedance analysis (BIA) is a novel and convenient method to measure body fat mass. The correlation between BIA and adenoma risk is unknown.

Aims: To conduct a cross-sectional study to evaluate BIA and other measures of obesity as risk factors for adenomas.

Methods: Participants underwent screening colonoscopy between 2006 and 2008. Waist-hip ratio (WHR) and body mass index (BMI) were measured. Percent body fat was calculated by BIA using a proprietary scale. Physical activity and other risk factors were assessed by telephone interview.

Results: 255 patients with adenomas and 679 adenoma-free subjects were included. Increased age, male sex, and decreased physical activity were associated with adenoma prevalence. In multivariate analysis, WHR and BMI were independently associated with adenoma prevalence. Patients in the highest tertile of WHR had an OR of 2.0 (95% CI 1.2-3.2) compared to the lowest tertile. Obese white patients had significantly increased odds of having adenomas (OR 2.0 (95% CI 1.3, 3.2)) compared to whites with a normal BMI. Percent body fat measured by BIA was not associated with adenoma status: patients in the highest tertile of percent body fat had an OR of 1.0 (95% CI 0.7-1.6) compared to patients with the lowest tertile.

Conclusions: Percent body fat calculated by BIA was not associated with adenoma prevalence. Although BIA is a quick and convenient measure of adiposity, it is not predictive of adenoma risk perhaps because it measures the amount of fat but not the distribution.