Obesity associated with abnormal bowel habits, not diet, researchers find

A team of physician researchers at Beth Israel Deaconess Medical Center (BIDMC) in Boston, Massachusetts found a strong association between obesity and chronic diarrhea independent of an individual's dietary, lifestyle, psychological factors, or medical conditions, according to a new study published in Alimentary Pharmacology & Therapeutics.

Using the 2009-2010 National Health and Nutrition Examination Survey (NHANES), a program of studies administered by the U.S. Centers for Disease Control and Prevention designed to assess the health and nutritional status of adults and children in the United States, researchers analyzed the bowel health questionnaire responses of 5,126 patients over the age of 20 years old who did not report a history of irritable bowel syndrome, celiac disease, or colon cancer. The team compared the reported bowel habits of patients who had a body mass index (BMI) associated with being underweight, normal weight, overweight, obese, and severely obese.

After controlling for dietary, physical activity, diabetes, laxative use, and demographic factors, the team found that respondents who were obese or severely obese were 60 percent more likely to have experienced chronic diarrhea compared to those with normal bowel habits or constipation.

The study reveals the association is not driven by compounding factors the team controlled for, however questions remain about what underlying causes may explain why obese individuals would be more likely than non-obese individuals to have diarrhea. One possible explanation may be related to the link between obesity and chronic low-grade inflammation, which may contribute to diarrhea. Future research clarifying this relationship and determining how obesity triggers inflammation could serve as a base for how physicians approach treating abnormal bowel habits with this patient population.

"While several previous studies have pointed to an association between obesity and bowel habits, all lacked data on whether dietary or other factors drive the connection," said corresponding author Sarah Ballou, PhD, a health psychologist in the Division of Gastroenterology, Hepatology, and Nutrition at BIDMC. "Our research confirms a positive association between obesity and chronic diarrhea and reveals for the first time that this relationship is not driven by confounding factors such as diet or physical activity level."