Late-night eating, stress tied to bowel issues

High physiological stress combined with late-night eating was associated with a higher likelihood of abnormal bowel habits and reduced gut microbial diversity, according to a two-cohort analysis of more than 15,000 patients.

“We all know that stress can wreak havoc on our digestive system,” lead study author Harika Dadigiri, MD, a resident physician at New York Medical College at Saint Mary’s and Saint Clare’s Hospital, said during a press briefing in advance of Digestive Disease Week® (DDW) 2026. “But our study asked a more specific question: Does eating late at night make things worse?”

For the study, Dr. Dadigiri and colleagues analyzed data from the National Health and Nutrition Examination Survey (NHANES) and the American Gut Project (AGP) to examine how allostatic load and meal timing interact to affect gastrointestinal function. In the NHANES cohort of 11,149 patients, higher allostatic load—defined by a composite score of cardiovascular, metabolic, and inflammatory biomarkers—was linked to a 1.32 times higher likelihood of abnormal bowel habits, including constipation or diarrhea. Late-night eating, defined as consuming more than 25% of daily calories after 9 p.m., made this association even stronger.

Patients who had both high stress and ate late at night had the highest rate of abnormal bowel habits (39%). In comparison, only 23% of patients with low stress who ate earlier had these issues. Multivariable models adjusted for age, sex, and poverty-income ratio supported these findings.

In the second phase, researchers studied 4,157 patients from the AGP dataset to confirm a “high stress plus poor diet” pattern based on what patients reported about their mental health, sleep, and eating habits. This group had 2.5 times the odds of abnormal bowel function compared with healthier counterparts. Microbiome testing using 16S ribosomal RNA sequencing showed that these patients had lower gut bacteria diversity, measured by the Shannon index, with a modest but statistically significant reduction compared with controls.

This finding indicates that meal timing “might magnify the impact of stress on the microbiome via the gut-brain axis,” Dr. Dadigiri explained. “It also suggests that a combination of stress and late-night eating doesn’t just affect how you feel in the bathroom, it may also be reshaping the ecosystem of bacteria living in your gut.”

Dr. Dadigiri said that the overall study findings support ongoing evidence of the “chrononutrition-stress axis,” the idea that “lifestyle interventions addressing both the stress management and mealtime optimization may help improve gut health. This research also adds another dimension to our understanding of gut health, suggesting it’s not just what you eat, it might also be when you eat and how stressed you are when you do.”

She acknowledged that the study’s observational design highlights associations rather than cause-and-effect relationships. As a next step, she and her colleagues aim to carry out longitudinal studies that track individuals over time to gain deeper insight into late-night eating patterns.

Dr. Dadigiri reported having no financial disclosures.

DDW is AGA's annual meeting, jointly sponsored by AGA, AASLD, ASGE, and SSAT. Learn more at ddw.org.