According to the Crohn’s and Colitis Foundation, creeping fat occurs when mesenteric fat, the kind that naturally develops in the abdominal area, wraps around the bowel wall, causing it to thicken. Creeping fat can cover as much as half the intestine. “Under normal conditions fat sits right next to the intestine rather than wrapping around it as we see in patients with Crohn’s disease,” says Charalabos Pothoulakis, MD, PhD, the director of basic research at the UCLA Center for Inflammatory Bowel Diseases in Los Angeles. While creeping fat shares features with the fat associated with obesity, it has more fat cells, and those fat cells are smaller. RELATED: 10 Things Doctors Want You to Know About Managing Crohn’s Disease
How Creeping Fat Interacts With Crohn’s
According to an article published in October 2018 in the journal Inflammatory Bowel Diseases, adipose tissue is an important part of the body’s endocrine system, a network of glands and organs that release proteins and chemical signals, including hormones. Hormones are involved in a lot of what goes on in our bodies, from simple feelings like hunger to more complex emotions and even functions like metabolism and reproduction. Hormones affect both the immune system and the intestinal cells, which is how doctors believe creeping fat interacts with Crohn’s. But creeping fat is still largely an enigma. “We know very little about why creeping fat forms and what it does,” says Florian Rieder, MD, a researcher in the department of pathobiology and a gastroenterologist at Cleveland Clinic in Ohio. In general, Dr. Rieder says, creeping fat is hard to investigate because it cannot be sampled during a colonoscopy; researchers can only take it from a section of intestine that has been removed from the body. Plus, since creeping fat exists exclusively in people with IBD, it’s not possible to create a study with a control group of people who have creeping fat but not IBD. What we do know, says Rieder, is that creeping fat contains a lot of inflammatory cells, an indication of an inflammatory response occurring in the body, and that creeping fat appears to have a negative effect on IBD. RELATED: ‘You Have Crohn’s Disease’: Advice for Dealing With a New IBD Diagnosis
Why Creeping Fat Is a Problem
A review published in June 2019 in the journal Cells determined that creeping fat can make IBD therapies less effective and drive disease progression. The researchers, led by Piotr Eder, MD, PhD, a gastroenterologist at Heliodor Święcicki Hospital at the Poznań University of Medical Sciences in Poland, found that the cells in creeping fat are immunoregulatory (meaning the chemicals they release regulate the immune system) as well as pro-inflammatory (meaning the cells promote inflammation). The findings of another report, published in February 2019 in the journal Pharmacological Reports, suggest that creeping fat releases a protein called cytokine, which is vital to the function of organs but also causes inflammation. According to Dr. Pothoulakis, this is the reason creeping fat may inhibit the gut from responding to anti-inflammatory therapies. The cells in creeping fat continue to release inflammation-promoting signals into the intestines even when medication is working to calm inflammation. It’s like trying to remove water from a flooding basement while water is still pouring in. But while creeping fat can intensify gut inflammation, at times it seems to have a protective effect. It all depends on the phase of the inflammation, says Pothoulakis. “Crohn’s disease is a disease that has peaks and valleys,” he explains, and those fluctuations change creeping fat’s role. “Creeping fat becomes inflamed when the bowel is inflamed and makes CD worse,” he says, but on the flip side, it appears that creeping fat can help soothe inflammation when a flare-up is in remission. RELATED: How to Find Relief During a Crohn’s Flare
The Complications of Creeping Fat
According to Rieder, the inflammation associated with creeping fat can result in abdominal pain, diarrhea, bloating, cramping, and blood in the stool — many of the same symptoms associated with a disease flare-up. Creeping fat can lead to fibrostenosis, a common complication that affects around one-third of all patients with Crohn’s disease. Fibrostenosis causes strictures (a narrowing of sections of the intestine that leads to blockages) and intestinal fibrosis, a buildup of scar tissue that causes inflammation. According to the Cleveland Clinic, more than 80 percent of people with Crohn’s disease who develop intestinal strictures have creeping fat in the same spot. Rieder explains that anything that drives chronic inflammation, as creeping fat appears to do, increases a person’s risk of developing intestinal fibrosis. He says that creeping fat can also cause internal penetrating disease, which manifests as fistulas (holes or ulcers) in two parts of the intestines that connect to each other, or the section of the intestine that connects to skin, such as the rectum. Fistulas prevent the intestine from working properly so it doesn’t absorb as many nutrients as it should. The complication often requires an operation in which a surgeon removes the damaged parts of the intestines and reattaches the two healthy ends together. A study that included 90 people with Crohn’s disease, published in January 2019 in the journal Digestive Diseases and Sciences, found that 21 percent had creeping fat, confirmed by MRI, a type of scan that uses magnets to create images inside the body. Focusing on the subjects with creeping fat, the researchers discovered that nearly 80 percent of the males and almost 70 percent of the females eventually developed bowel damage. On average, roughly half these patients required surgery within two years of being diagnosed with creeping fat. The researchers concluded that creeping fat increases complications associated with Crohn’s disease, including bowel damage and surgery. Pothoulakis notes that while certain scans can detect the presence of creeping fat, the only way to know how much fat there is and how tightly it’s constricting the bowel is to see it in the flesh. He adds that surgery is only necessary when a person with creeping fat does not respond to medication. RELATED: The Dangers of Untreated Crohn’s Disease
Minimizing the Dangers of Creeping Fat
Because doctors aren’t sure why creeping fat forms, it’s difficult to determine what people can do to reduce their risk of developing it. “One can hypothesize that controlling the disease through medication and other therapies can decrease the risk of complications, as well as prevent this quite mysterious tissue from forming in the abdomen,” says Dr. Eder. “The most important thing for all patients with Crohn’s disease to do, regardless if there are signs of creeping fat, is to control inflammation through medication and a healthy diet and lifestyle.” Obesity is not tied to creeping fat, but it is linked to an increased need for surgery if you have IBD. “In a large number of patients, we see a direct link between obesity and increased inflammation in Crohn’s disease,” Pothoulakis says. “Research [published in Nutrients in February 2019] has shown that if you are obese, you are more likely to go to surgery if you have CD, which suggests that if you’re obese, you will likely have a worse outcome of your CD compared with other patients who are a healthy weight.” There is still a lot we don’t know about creeping fat and the effect it has on Crohn’s disease, but researchers around the world are making progress. “We learn more about creeping fat on a daily basis, and further understanding may lead to recommendations in the future,” says Rieder.
