Can interval fasting protect gut health?

In a new study recently presented at the annual meeting of the American Physiology Summit in Long Beach, California, researchers from the Arizona College of Osteopathic Medicine at Midwestern University in Downers Grove, Illinois, reported that interval fasting may also help protect the gastrointestinal system-primarily the small intestine-as we age.

The researchers used a mouse model that they genetically modified to accelerate aging. One group of mice had food available all the time, while the other group had access to food only during alternating 24-hour cycles.

After 8 months, the scientists found that the mice that had fasted gained less weight and had structural changes in the small intestine associated with better glucose control and reduced inflammation.

"Our study shows that interval fasting is a beneficial dietary practice for weight control, improving blood glucose levels and positively affecting the gut by reducing inflammation and oxidative stress while altering gut structure," Spencer Wrogop, a second-year student at the University of Arizona. Midwestern University College of Osteopathic Medicine and first author of this study.

How does aging affect the small intestine?

In this study, the researchers focused on a specific part of the small intestine called the jejunum.

The jejunum is the second of the three sections of the small intestine, responsible for continuously digesting food and absorbing nutrients and water from food so that they can be utilized in other parts of the body.

"As mammals age, devastating changes occur in the morphology of the small intestine that affect its ability to absorb nutrients and maintain its structure," Vrohop explained.

"Our study shows that interval fasting can help prevent these age-related changes by returning the jejunum to a 'younger' version," he told us.

Effects of interval fasting in men and women

At the end of the study, the researchers noticed that the improvement in the health and appearance of the small intestine was more pronounced in female mice than in males.

However, the scientists found that the effect of interval fasting on blood sugar levels was stronger in male mice than in female mice.

In the next phase of the study, researchers plan to dig deeper into what may be behind these gender differences.

What do you need to know about interval fasting?

Interval fasting is a schedule of eating at certain times followed by not eating for an extended period of time, a period known as fasting, when a person abstains from food.

The several different methods of interval fasting depend on how many hours or days the fast lasts, how many hours or days a person can eat, and how many calories they can consume.

Some of the most popular interval fasting regimens include time-limited eating, where fasting lasts 12, 14, or 16 hours and the eating period is stretched out over the remaining hours of the day, or the 5:2 method, where a person consumes only 500 calories for 2 days a week and then eats normally for the remaining 5 days.

According to the International Food Information Council's 2023 Food and Health Survey, about 12% of American adults follow interval fasting as their diet or eating pattern, making it currently one of the most popular diets.

In addition to weight loss, recent studies show that interval fasting can bring other health benefits, such as protection against type 2 diabetes, cardiovascular disease and cancer, as well as gastrointestinal problems such as inflammatory bowel disease and ulcerative colitis.

Is interval fasting safe?

Rudolph Bedford, M.D., a board-certified gastroenterologist at Providence St. John's Health Center in Santa Monica, California, who was not involved in the recent study, said that while interval fasting may help gastrointestinal health in some ways, it can also potentially cause problems.

"Essentially, the body needs to be able to burn calories over a period of time, not intermittently, so to speak," Bedford explained. "So a person really needs to eat."

"I think some people will [...] eat for a few days and then fast for a couple days, limiting their calorie intake to about 500 calories for the whole day," he continued. "I don't have a problem with that. I think longer periods of fasting can be somewhat detrimental to your system and your body."

According to Bedford, interval fasting can be helpful in protecting against the development of diseases such as diabetes and irritable bowel syndrome (IBS).

And, he added, by doing interval fasting, "you can essentially give your body a break, so to speak, in terms of having to work and burn calories or absorb nutrients in different ways."

What type of interval fasting is best?

For those beginning interval fasting, the number of methods can be a bit overwhelming and confusing.

When asked which method of interval fasting is best, Ali said that there is no single best method because what works for one person may not work for another.

Nevertheless, he advised:

"I suggest patients start with simpler ways, such as overnight fasting - stop eating after 8 p.m. At night. And don't eat until 8 a.m. The next morning. That's a little easier to do because most of the time you're asleep and you don't feel hunger as much. And then you can increase that time to longer periods of time."

"Some people find benefit in intermittent fasting on a daily basis, where you eat one day and don't eat another day, and that's fine too," Ali added. "It's a trial and error method to determine which method works best for you."