Stress and Late-Night Eating Combined with Stress Linked to Abnormal Bowel Habits and Reduced Gut Microbial Diversity

At Digestive Disease Week, researchers reported that participants with chronic stress who ate >25 % of daily calories after 9 p.m. were up to 2.5 times more likely to have constipation or diarrhea. Prior work linked late-night eating to sleep, diabetes, obesity and GERD, but not to gut microbiome changes. Risk rose only when stress and late-night eating co-occurred; late-night eating alone showed no effect.

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The study merged data from 11,149 adults in the 2005-2010 NHANES and >4,100 participants in the 2013-2017 American Gut Project (Microsetta Initiative). Stress was measured by an allostatic load score combining eight cardiovascular, metabolic and inflammatory biomarkers. In the stressed-late-night-eating group, bowel irregularities increased 2.5-fold and gut-microbiome diversity was markedly lower than in others.

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Dr. Geoffrey Preidis, associate professor of pediatrics at Baylor College of Medicine, said stress and excess late-night eating often coincide, raising risk, and described the gut microbiota as intestinal organisms, noting that diverse microbiomes “bounce back readily from disruptions.” Dr. William Chey, president of the American College of Gastroenterology, called the results hypothesis-generating and urged more research on meal timing as a risk factor. Dr. Kyle Staller, director of Gastrointestinal Motility Laboratory at Massachusetts General Hospital, advised avoiding food within three to four hours before bedtime to permit gastric emptying and reduce reflux.

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As a cross-sectional analysis, the study cannot prove causality, and the direction between microbiome shifts and bowel symptoms is unclear. The data lack details on food types, medication use and medical conditions, which could confound results. Experts warned that ultraprocessed foods common in late-night meals are independently linked to bowel irregularities.

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• “I’m a person who myself eats a lot of times late at night, so it was just out of curiosity, and I couldn’t find a lot of articles about it,” — Dr. Harika Dadigiri, lead author, resident physician at New York Medical College

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• “This is important because stress and excess late-night eating often go hand in hand,” — Dr. Geoffrey Preidis, associate professor of pediatrics, Baylor College of Medicine

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• “These findings should be viewed as hypothesis generating and spur additional research to better understand whether meal timing might be a modifiable risk factor in patients with constipation or diarrhea,” — Dr. William Chey, president, American College of Gastroenterology

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• “Generally, not eating in the three to four hours before bedtime is best so there’s ample time for food to empty from the stomach, said Dr.” — Dr. Kyle Staller, director, Gastrointestinal Motility Laboratory, Massachusetts General Hospital

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The research team plans longitudinal studies to test whether restricting evening caloric intake can improve bowel regularity and restore microbial diversity, potentially informing future clinical guidelines for functional gastrointestinal disorders.

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