Leaking bacteria from the intestine triggers "creeping fat" that often occurs in people with Crohn's disease, according to a new study.

Creeping fat is abdominal fat that wraps around the intestines of patients with this type of inflammatory bowel disease (IBD). It was unknown what triggered the fat to do this.

"Creeping fat is often a landmark for surgeons performing resections on an IBD patient's bowels because they know when they see it, that's likely where the lesions are located," said study author Suzanne Devkota, an assistant professor of gastroenterology at Cedars-Sinai in Los Angeles.

"But we don't know whether the presence of the fat is making the disease worse or trying to protect the intestines from something," she added in a hospital news release.

Devkota's team analyzed small intestine and fat tissue samples from 11 Crohn's patients who had gone through surgery. Along with storing energy, fat (adipose tissue) contains immune cells that appear to be triggered in certain cases of IBD.

"We found that the adipose tissue is actually responding to bacteria that have migrated out of the patient's damaged intestines and directly into the fat," Devkota said. "We believe the 'creeping' migration of the fat around the intestines is intended to try and plug leaks in the diseased organ to prevent the gut bacteria from getting into the bloodstream."

But creeping fat may contribute to severe intestinal scarring (fibrosis) that occurs in 40% of Crohn's patients, according to the researchers. In many of these cases, surgical removal of parts of the small intestine is the only option.

Patients with ulcerative colitis, the other most common IBD, don't develop creeping fat, the authors said. Their study was recently published in the journal Cell.

Researchers also pinpointed a specific type of bacteria (Clostridium innocuum) that prompts fat to travel to the small intestine and encase it, imperiling its function. The finding could lead to new treatments.

"We've identified a specific infectious agent that can trigger a process that makes Crohn's worse. This is a critical step toward the development of therapies that target C. innocuum, allowing us to prevent or minimize the damaging effect of creeping fat," said Dr. Stephan Targan, director of Cedar-Sinai's Inflammatory Bowel and Immunobiology Research Institute.