Intermittent fasting could reshape gut bacteria and boost liver health

May 1, 2021
Intermittent fasting's benefits go far beyond any weight loss. (AP Photo/J.M. Hirsch)

Intermittent fasting's benefits go far beyond any weight loss. (AP Photo/J.M. Hirsch)

The health benefits of intermittent fasting could be partly due to changes in certain gut bacteria, according to researchers who looked at people who fasted for the Islamic holy month.

In a study published April 12 in The American Journal of Clinical Nutrition, participants who abstained from eating or drinking for 16 hours each day during Ramadan had microbiomes different from those before the fasting period and compared with those who didn't fast. People who fasted also had improved measures of liver health, which researchers suggest could be due to a greater abundance of Lachnospiraceae bacteria.

"Intermittent fasting is a dietary concept in which people don't necessarily eat less, but they increase the time between meals," said senior author Maikel Peppelenbosch, a professor of gastroenterology and hepatology at the Erasmus University Medical Center, in the Netherlands. "It can take many forms, and many people do it for medical reasons or social reasons or, in the case of Ramadan, for religious reasons."

Intermittent fasting, which involves eschewing food for certain hours of the day or periods during the week, has gained popularity in recent years due to its purported health benefits, including weight loss, improved metabolism and a reduced risk of diseases such as diabetes. 

But exactly how this diet improves health isn't entirely clear, according to Peppelenbosch, although other studies in rodents and humans indicate that the gut microbiome could play a role. Intestinal microbes can influence many parts of the body, including the immune system, the brain and the heart.

To dig into the links between intermittent fasting and gut bacteria, Peppelenbosch and his colleagues looked at people who abstained from consuming food and beverages for about 16 hours per day between dawn and dusk during the month of Ramadan, the timing of which varies from year to year because the Islamic calendar follows moon cycles.

"If you talk about religious fasting, Ramadan is the biggest on the planet. More than a billion people do this to a certain extent each year. But remarkably little is known about what is happening to these people," Peppelenbosch told The Academic Times. "We set up a study in which people either would participate as they normally do in Ramadan, and we followed them before, during and after Ramadan, or we asked them for one year not to participate in Ramadan so we could also compare them."

The researchers looked at two different groups: a middle-aged cohort including 27 people who fasted, and 10 nonfasting control subjects; and a cohort of 30 young males, all of whom fasted. To evaluate the gut microbiome, the researchers analyzed participants' stool samples and also measured body weight and took blood samples. 

In both cohorts, the researchers saw shifts in the composition of bacteria between the start and the end of the fasting period, changes that were not seen in the nonfasting people. According to Peppelenbosch, these findings agree with other studies that have found that intermittent fasting, including the Ramadan version of this diet, remodels the gut microbiome.

After 30 days of fasting, participants in both age groups lost weight, indicated by lower body mass and body fat percentage. In addition, middle-aged people who fasted showed improved measures of liver health compared with the period before the fasting and in comparison to their nonfasting counterparts.

"What we were most excited about was that the condition of the liver improved so much," Peppelenbosch said. "When people participated in Ramadan, the liver apparently went into better condition as judged from the liver enzymes." 

Peppelenbosch suspects that these effects are due to changes to gut bacteria. In the middle-aged group, the researchers saw big increases in the abundance of Lachnospiraceae bacteria at the end of Ramadan, a difference that wasn't seen in the nonfasting control group. This group of bacteria produces a compound called butyrate, which is important for intestinal health as well as metabolism, immunity and brain function.

"We interpret these findings based on available scientific literature indicating that butyrate-producing bacteria improve the condition of the liver because they release butyrate, which moves from the intestine into the liver," Peppelenbosch explained. "The liver sees this butyrate and thinks 'Let's start breaking down liver fat.' The physical presence of fat in the liver is actually a major cause of liver [disease]."

Although there was a link between butyrate-producing Lachnospiraceae and liver enzyme levels, more research is needed to establish whether the microbiome was responsible for these changes, Peppelenbosch said.

When the researchers looked at the middle-aged participants 30 days after the end of the fasting period, they found that most measures of liver health and gut bacteria returned to pre-Ramadan levels, suggesting that health benefits of this type of intermittent fasting may be short-lived.

It's not clear whether the effects seen in this study would apply to people following other types of intermittent fasting or be consistent across all people observing Ramadan. Although the researchers looked at gut bacteria of two different age groups, they didn't evaluate liver health measures in the young male cohort. Another limitation of the study, Peppelenbosch said, is that the team looked at only gut bacteria and didn't consider other gut-dwelling microbes, such as fungi.

The paper is the first publication from a larger study that also aims to examine the effects of Ramadan fasting on people with conditions such as Type 2 diabetes, morbid obesity and heart disease, according to Peppelenbosch. In addition, he and his colleagues are conducting other studies to look at the effects of other types of intermittent fasting on inflammatory bowel disease and cancer. 

In the future, Peppelenbosch hopes that better understanding of the effects of fasting could help inform dietary recommendations to help manage diseases or prevent disease in healthy people.

The study, "Remodeling of the gut microbiome during Ramadan-associated intermittent fasting," published April 12 in The American Journal of Clinical Nutrition, was authored by Junhong Su, Erasmus MC—University Medical Center Rotterdam and Kunming University of Science and Technology; Yueying Wang and Zhongren Ma, Northwest Minzu University; Xiaofang Zhang, Kunming University of Science and Technology; Mingfu Ma, The Fifth People's Hospital of Qinghai (Qinghai Tumor Hospital); Zhenrong Xie, First Affiliated Hospital of Kunming Medical University; Qiuwei Pan and Maikel P. Peppelenbosch, Erasmus MC—University Medical Center Rotterdam.

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