What is irritable bowel syndrome?

Irritable bowel syndrome (IBS) is a condition that causes a person to experience uncomfortable gastrointestinal (GI) symptoms on a regular basis. These can include:

  • stomach cramping
  • pain
  • diarrhea
  • constipation
  • gas
  • bloating

Symptoms for IBS can range from mild to severe. The difference between IBS and other conditions that cause similar symptoms — such as ulcerative colitis and Crohn’s disease — is that IBS doesn’t damage the large intestine.

It’s not typical to have weight loss because of IBS, unlike ulcerative colitis and Crohn’s disease. However, because IBS can impact the type of foods a person can tolerate, it may result in weight changes. There are steps you can take to maintain a healthy weight and live well with IBS.

According to the Cleveland Clinic, IBS is one of the most common disorders that affects the functioning of the GI system. Estimates vary but they say that as much as 20 percent of adults in the United States have reported symptoms that are synonymous with IBS.

The exact causes of IBS are unknown. For example, some people with IBS experience increased bouts of diarrhea because their intestines seem to move food through faster than normally. In others, their IBS symptoms are associated with constipation due to a gut that moves more slowly than normal.

IBS can result in weight loss or gain in certain individuals. Some people may experience significant abdominal cramping and pain that may cause them to eat fewer calories than they normally would. Others may stick to certain foods that contain more calories than needed.

Recent research has indicated that there may also be a connection between being overweight and having IBS. One theory is that there are certain hormones made in the digestive tract that regulate weight. These five known hormones appear to be at abnormal levels in people with IBS, either higher or lower than expected. These changes in gut hormone levels may affect weight management, but more research is still needed.

You may not always be able to control your symptoms when you have IBS, but there are some ways to help you maintain a healthy weight, including eating a healthful diet that includes fiber.

A diet that involves eating several small meals is recommended over eating large meals when you have IBS. In addition to this rule of thumb, a diet low in fat and high in whole grain carbohydrates can also benefit you when you have IBS.

Many people with IBS are hesitant to eat foods that have fiber for fear they’ll cause gas that worsens symptoms. But you don’t have to avoid fiber completely. You should slowly add fiber to your diet, which helps reduce the likelihood of gas and bloating. Aim to add between 2 to 3 grams of fiber per day while drinking plenty of water to minimize symptoms. An ideal daily amount of fiber for adults is between 22 and 34 grams.

You may want to avoid foods that are known in some people to worsen IBS — these foods also tend to result in weight gain. This includes:

  • alcoholic beverages
  • caffeinated beverages
  • foods with significant amounts of artificial sweeteners like sorbitol
  • foods known to cause gas, such as beans and cabbages
  • high-fat foods
  • whole milk products
  • fried foods

Your doctor may also recommend keeping a journal of the foods you eat to see if you can identify ones that tend to worsen your symptoms.

Another option for those looking to maintain a healthy weight and minimize IBS symptoms is a low FODMAP diet. FODMAP stands for fermentable oligo-di-monosaccharides and polyols. The sugars found in these foods tend to be more difficult for people with IBS to digest and they often worsen symptoms.

The diet involves avoiding or limiting foods that are high in FODMAPs, including:

  • fructans, found in wheat, onion, and garlic
  • fructose, found in apples, blackberries, and pears
  • galactans, found in beans, lentils, and soy
  • lactose from dairy products
  • polyols from alcohol sugars like sorbitol and fruits like peaches and plums

Reading food labels carefully and avoiding these additives can help you reduce the likelihood that you’ll experience stomach symptoms related to IBS.

Examples of IBS-friendly, low FODMAP foods include:

  • fruits, including bananas, blueberries, grapes, oranges, pineapples, and strawberries
  • lactose-free dairy
  • lean proteins, including chicken, eggs, fish, and turkey
  • vegetables, including carrots, cucumbers, green beans, lettuce, kale, potatoes, squash, and tomatoes
  • sweeteners, including brown sugar, cane sugar, and maple syrup

Those on a low FODMAP diet may eliminate some higher FODMAP foods and slowly add them back in to determine what foods can be safely eaten.

Weight loss or gain can be a side effect of IBS. However, there are diet approaches that can help you reduce your symptoms while maintaining a healthy weight.

If a dietary approach doesn’t help your symptoms, talk to your doctor about other potential causes of your weight loss or gain.