Obesity and IBS

Is obesity more common among people who have IBS? Or is IBS more prevalent among those who are obese? That’s the mystery a recent review of scientific literature set out to determine.

Approximately one-third of adults in the U.S. are obese. Obesity is defined as excess body fat and is associated with many other conditions, including those that affect the gastrointestinal tract. IBS occurs in up to 20% of adults in the U.S. Although the exact biological cause of IBS remains unknown, research has identified that abnormal intestinal motility (the movement of the intestines), diet, and an imbalance in the normal bacteria present in the gut may all be involved. Diets that are low in fiber, high in saturated fats, and high in fermentable carbohydrates may contribute to IBS in people who are obese. Fiber is important in the digestive process because it can increase the bulk of stools, which benefits constipation and diarrhea, common symptoms of IBS. Diets high in saturated fats have been linked to increased gut motility, contributing to diarrhea. Fermentable carbohydrates, such as fructose and lactose, create more gas, abdominal pain, bloating, nausea, constipation and diarrhea in people with IBS, and a diet low in FODMAP (fermentable oligosaccharides, disaccharides, monosaccharides and polyols) may reduce symptoms of IBS. In addition to diet, the alterations in gut bacteria in both obesity and IBS may be a common link between the two conditions. Researchers hope that uncovering the link between the two disorders may lead to a greater emphasis on weight loss interventions that also reduce IBS symptoms.

Is there a link between obesity and IBS?

The review searched through peer-reviewed published articles from 1980 to July 2012 to find studies that examined the relationship between excess body weight, or obesity, and IBS. Fifty-one articles were reviewed, and a total of 11 studies that fit the search criteria were included in the final analysis. Two of the studies were in pediatric (children), and nine of them were in adult participants. In the pediatric studies, one showed that obesity was significantly more common in children with IBS compared to children without IBS. However, the other study showed no link between the two conditions.

In the adult studies, the association was likewise mixed. Some studies showed a correlation between obesity and IBS, including one that identified an increase in IBS symptoms with increased BMI (body mass index, a measure of height and weight that is commonly used to determine obesity). One study also showed patients with IBS who underwent weight loss surgery, such as gastric bypass, showed an improvement in their IBS symptoms. However, other studies failed to identify a link between IBS and obesity, leading the analysis to conclude that the association between the two conditions remains unclear.

While the research community continues to study the possibility of a link between these two conditions, individuals who have both conditions can be their own advocate by talking to their healthcare team about these and all the symptoms they are experiencing. Many of the diets that can be helpful in managing IBS may also help in weight loss, and efforts to create a healthy gut flora (bacteria present in the intestines) can also help with digestive health for both conditions.

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