(HealthDay News) — Obesity is associated with significantly increased risks for incidence of colorectal adenoma and colorectal cancer in middle-aged and older men who are screened with sigmoidoscopy, according to research published online May 28 in the Journal of Clinical Oncology.

Cari M. Kitahara, Ph.D., of the National Institutes of Health in Rockville, Md., and colleagues prospectively evaluated the association between baseline body mass index (BMI) and risks for incidence of distal adenoma, recurrence of adenoma, and incidence of colorectal cancer. Among men and women, aged 55 to 74 years, who were screened with flexible sigmoidoscopy as part of the Prostate, Lung, Colorectal, and Ovarian Cancer Screening Trial, 1,213 cases of incident distal adenoma, 752 cases of recurrent adenoma, and 966 cases of incident colorectal cancer were detected.

The researchers found that the risks of incident adenoma (odds ratio [OR], 1.32) and incident colorectal cancer (hazard ratio, 1.48) were significantly higher in obese men (BMI, ≥30 kg/m²) compared with normal-weight men (BMI, 18.5 to 24.9 kg/m²). A non-significant positive association was found between obesity and recurrent adenoma in men (OR, 1.50; P trend = 0.07). No significant associations were found between obesity and either colorectal adenoma (incident or recurrent) or incident colorectal cancer in women.

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“Data from this large prospective study suggest that obesity is important throughout the natural history of colorectal cancer, at least in men, and colorectal cancer prevention efforts should encourage the achievement and maintenance of a healthy body weight in addition to regular screenings,” the authors write.