Obesity is thought to be associated with increased risk of colorectal polyps called adenomas, which can become cancerous, but weight loss might reduce this risk. To investigate the relation between obesity and the prevalence of colorectal polyps, researchers from Japan studied 7693 asymptomatic, average risk participants who underwent initial colonoscopy. A total of 2568 participants had second examination a year later. The researchers measured the body mass index of all the participants at the start and the end of the study. It was found that the prevalence of colorectal polyps at the initial colonoscopy increased proportionally with increasing body weight. Increasing body mass index, or BMI, was also found to be associated with increasing numbers of colorectal polyps, but not with the size or stage of the polyps. The incidence of polyps was lower in people who lost weight (10 percent) than in those who gained weight (16 percent) or maintained their weight (17 percent). The above findings indicate that though obesity is a risk factor for the development of colorectal adenoma, a reduction in body weight can decrease this risk.
American Journal of Gastroenterology
August 2008