If stress causes your digestive problems, eating late at night won’t do you any favors. In new initial research, thousands of participants who consumed more than 25% of their daily calories after 9pm in stressful situations were up to 2.5 times more likely to have abnormal bowel habits, such as constipation or diarrhea.
The study is a summary that has not yet been peer-reviewed or published in a scientific journal, but was presented in May at Digestive Disease Weeka prestigious annual meeting for professionals in gastroenterology, hepatology and related areas. The research was also observational, as all data was collected at a single moment; therefore, it does not prove a causal relationship between stress, night eating and intestinal health.
“I myself am a late-night eater, so it was just out of curiosity, and I didn’t find many articles on the subject,” said lead author Dr. Harika Dadigiri, explaining why she carried out the research. Most studies on the health effects of eating late at night focus on sleep, diabetes, obesity, and acid reflux or GERD (gastroesophageal reflux disease).
Dadigiri and his co-authors analyzed the health data of 11,149 participants collected from 2005 to 2010 from the U.S. Centers for Disease Control and Prevention’s National Health and Nutrition Examination Survey (NHANES). The researchers also included more than 4,100 patients from the 2013 to 2017 period of the American Gut Project, now called the Microsetta Initiative.
The latest data did not contain all the details the authors wanted, said Dadigiri, who is also a resident physician at New York Medical College, Saint Mary’s General Hospital and Saint Clare’s Denville Hospital, both in New Jersey.
“Few previous studies have explored the impact of meal timing, or the combination of stress with late-night eating, on intestinal function,” Dr. Geoffrey Preidis, associate professor of pediatrics in the division of gastroenterology, hepatology and nutrition at Baylor College of Medicine and Texas Children’s Hospital, said in an email.
“This is important because stress and late-night overeating often go hand in hand,” added Preidis, who was not involved in the research.
Meal times and the gut
In the new research, the authors defined chronic physiological stress by participants’ allostatic load composite score — which involves eight cardiovascular, metabolic and inflammatory biomarkers, such as blood pressure, cholesterol and body mass index.
Eating late at night alone did not affect health or bowel function, indicating that the combination with stress may be “the danger,” Daigiri noted in his presentation.
The researchers’ analysis of American Gut Project participants revealed that both late-night eating and high levels of stress were associated with a significantly lower diversity of bacteria in their gut microbiome.
“A is the set of all organisms — including bacteria, viruses and fungi — that live in the intestines,” Preidis said. Highly diverse gut microbiomes “recover more easily from perturbations, including illness, medication or other stressors,” he added.
According to Preidis, different gut microbes also contribute to our health in several ways, including optimizing nutrient absorption from food, regulating the immune system, and communicating with the brain to control sleep and mood.
Because the study is observational, it’s unclear whether the findings about the gut microbiome were causing gut problems or if abnormal gut function altered the gut microbiome, Preidis said.
There are also several important and potentially influential factors that the authors did not have data on, Dr. William Chey, president of the American College of Gastroenterology, said in an email. There may be differences between the foods consumed by people who ate earlier and the foods consumed by people in the evening.
If evening meals consisted of ultra-processed foods, for example, this has been linked to frequent intestinal problems such as constipation, said Chey, chief of the division of gastroenterology and hepatology at Michigan Medicine. The survey also lacked details about possible medical conditions or medication use.
“These findings should be viewed as hypothesis-generating and should stimulate additional research to better understand whether meal timing may be a modifiable risk factor in patients with constipation or diarrhea,” Chey said.
However, if future research finds a causal relationship, there are several possible explanations, Preidis said. “Both the body and the gut microbiome have natural circadian rhythms that can be disrupted by changes in diet composition or timing. These disruptions can affect hormones, immune activation, and motility of the stomach and intestines.”
Motility refers to how food moves through the digestive tract.
A 2024 study found that limiting eating to between 9 a.m. and 5 p.m. can reduce intestinal inflammation, which can lead to gut dysbiosis, an imbalance in the gut microbiota, Dadigiri said. Elevated levels of the stress hormone cortisol alone can also cause this imbalance.
Best Bedtime Practices
While the summary itself isn’t enough to offer specific lifestyle recommendations, these experts have advice that’s good for gut health and other health concerns.
In general, it’s best not to eat in the three to four hours before bedtime to give your stomach enough time to digest, said Dr. Kyle Staller, director of the Gastrointestinal Motility Laboratory at Massachusetts General Hospital and associate professor of medicine at Harvard Medical School.
Otherwise, the body must divert energy from other important processes that occur during rest to a digestive tract that should be inactive, said Staller, who was not involved in the research. Limiting nighttime eating can also help prevent acid reflux.
If you must eat at night, try to avoid high-fat foods, and keep portions small, Staller and Preidis said. Low-fat foods, such as fruits, complex carbohydrates, vegetables, and certain proteins, tend to be digested more quickly.
