Intermittent fasting is an eating pattern in which a person eats only during a certain number of hours and fasts for the rest of the day, often immediately following dinner through to part of the next day. Research has shown that intermittent fasting can help some people regulate their blood sugar levels, lose weight, and be healthier overall. According to a review published in December 2019 in the New England Journal of Medicine, fasting for 18 hours a day can improve the ability to manage stress, increase life span, and reduce risk for a number of health problems, including obesity and several cancers. But just because there are some studies backing up the benefits, it doesn’t necessarily mean intermittent fasting is right for everyone — especially people with inflammatory bowel disease (IBD), such as Crohn’s. Here’s why people with Crohn’s may want to steer clear of this diet trend. “Some studies have shown that intermittent fasting/time-restricted feeding may decrease inflammation and improve gut microbiome health,” says Kelly Kennedy, a registered dietitian nutritionist with Everyday Health. “But this research is still in its infancy.” Lack of research aside, many experts believe that people with Crohn’s disease shouldn’t try IF, partly because they may already be deficient in certain nutrients or underweight. Some studies have suggested that fasting in general — though not intermittent fasting itself — can lead to nutrient deficiencies, including protein. This is what an analysis published in October 2020 in the journal Nutrients found. “Limiting the amount of time you eat each day — or even the number of days per week — also limits the number of opportunities you have to get calories, vitamins, and minerals into your body,” she says. “This isn’t a good idea for anyone who is underweight.” Many people with IBD are also severely deficient in vitamin D, says Jill Gaidos, MD, a gastroenterologist at Yale New Haven Health in Connecticut and the director of clinical research for Yale’s IBD program. While vitamin D can be hard to get from food — it’s called the “sunshine vitamin” because your body makes it when you’re exposed to the sun — it can be found in fortified dairy foods, such as milk and yogurt. But people with IBD may avoid dairy products because they have trouble digesting lactose, a naturally occurring sugar found in dairy. People with IBD can also be iron deficient, because they’ve eliminated meat from their diet, she explains. About 1 in 3 people with IBD have anemia, a condition in which a person has less blood that can carry oxygen throughout the body, according to the Crohn’s & Colitis Foundation. The most common cause of anemia is low levels of iron.
Should You Try Intermittent Fasting if You Have Crohn’s?
Given the possible drawbacks of IF, experts are hesitant to recommend it for people with Crohn’s disease. This is especially true for people with severe Crohn’s who are unable to eat as much as they need to during a flare, explains Jeff D. Scott, MD, a gastroenterologist with Digestive Disease Specialists, Inc., and in private practice in Oklahoma. Sabine Hazan, MD, a gastroenterologist and creator of ProgenaBiome — a genetic sequencing research lab — says that if people with Crohn’s want to try IF to see if it reduces their symptoms, they should alert their doctor first. “If a Crohn’s patient is trying intermittent fasting, I would certainly recommend working with a registered dietitian nutritionist who specializes in digestive conditions,” says Kennedy. “It’s important that their weight and diet be tracked even more closely than usually recommended while on IF.” If fasting is causing you to lose out on vitamins and minerals or complicating your Crohn’s symptoms, you should stop, she says. Even if you are modifying your diet to better control your symptoms, keep in mind that it’s not a substitute for medications and shouldn’t be used to treat intestinal inflammation, Dr. Gaidos says. Rather than fast, Gaidos tells people who have Crohn’s to eat a well-balanced, healthy diet that is low in processed foods and sugar. Diets lower in indigestible fiber may also be easier for your body to digest, says Dr. Scott.
