Obesity affects approximately 40 percent of Americans, according to the U.S. Centers for Disease Control and Prevention. While obesity is known to be associated with increased risk of health conditions, such as heart disease, diabetes and gastrointestinal diseases, less is known about the relationship between obesity and abnormal bowel habits.

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In a comprehensive analysis of the relationship betweenbody mass index and bowel habits,published inAlimentary Pharmacology and Therapeutics,a team ofphysician-researchers at Harvard Medical School and Beth Israel Deaconess Medical Center found a strong association between obesity and chronic diarrhea independent of an individuals diet, lifestyle, psychological factors or medical conditions.

The findingscould have important implications for how physicians might approach and treat symptoms of diarrhea in patients with obesity.

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 authorSarah Ballou, HMS instructor in medicine and a health psychologist in the Division of Gastroenterology, Hepatology and Nutrition at Beth Israel Deaconess.

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, Ballou said.

Using the 20092010 National Health and Nutrition Examination Surveya program of studies administered by the CDC designed to assess the health and nutritional status of adults and children in the United StatesBallou and colleagues analyzed the bowel-health questionnaire responses of 5,126 patients over the age of 20 years 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 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.

While the study reveals the association is not driven by confounding factors the team controlled for, questions still remain about what underlying causes may explain why obese individuals would be more likely than nonobese individuals to have diarrhea.

One possible explanation may be related to the link between obesityand chronic low-gradeinflammation,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.

The treatment of obesity and obesity-related medical conditions requires multidisciplinary management, said senior authorAnthony Lembo, HMS professor of medicine and gastroenterologist in the Division of Gastroenterology, Hepatology and Nutrition at Beth Israel Deaconess.

Clinicians should be aware of the relationship between obesity and diarrhea, especially considering the potential negative impacts altered bowel habits can have on quality of life, Lembo said.

This work was supported by the National Institutes of Health (grant no. T32DK007760).

The authors declare no conflicts of interest associated with their manuscript.

Adapted from a Beth Israel Deaconessnews release.

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