Late-night eating combined with high or chronic stress levels can wreak havoc on the gastrointestinal (GI) system, according to the results of a new study.
“It’s not just what you eat, but when you eat it,” said first author Harika Dadigiri, MD, resident physician at New York Medical College at Saint Mary’s and Saint Clare’s Hospital, New Jersey, in a press briefing, which will be presented at Digestive Disease Week (DDW) 2026.
“While stress alone degrades gut function, the combination of high allostatic load and late-night eating creates a ‘double hit’ associated with pronounced bowel dysfunction and gut dysbiosis,” she said.
Chronic physiological stress and sleep and circadian disruptions are well established as having independent effects on GI dysfunction; however, less is known regarding meal timing and such effects.
Stress and Eating Patterns
To investigate the role of late-night eating in worsening the GI effects of chronic stress and gut dysbiosis, Dadigiri and her colleagues conducted a two-phase study, including 11,149 participants in the National Health and Nutrition Examination Survey study from 2005-2010 (phase 1), and 4,157 in the American Gut Project (AGP; phase 2).
The phase 1 evaluation looked at the relationship between chronic physiological stress, as represented by the Allostatic Load Score (ALS) — a composite of eight cardiovascular, metabolic, and inflammatory biomarkers — and late-night eating, defined as consuming more than 25% of daily calories after 9 PM.
The Bristol stool scale was then used to assess gut outcomes, with adjustments for confounders including age, sex, and poverty-income ratio.
The phase 2 data from AGP included self-reports of mental health, sleep, and eating patterns, in which patients meeting a profile of a high-stress/poor diet phenotype were identified.
That evaluation also assessed participants’ gut microbiota using 16S ribosomal RNA gene sequencing, with a focus on Alpha diversity (Shannon index) and specific taxa abundance.
In the phase 1 evaluation, having a high chronic stress or allostatic load (ALS ≥ 5) was significantly associated with a higher likelihood of having abnormal bowel habits, including constipation or diarrhea (odds ratio [OR], 1.32; P = .004).
In addition, participants who reported having high stress in addition to late-night eating habits had the highest prevalence of abnormal bowel habits (39.3%) compared to those with a low-stress/normal eating baseline (23.2%), representing a 1.7-fold absolute risk increase.
In phase 2, a “high stress/poor diet” phenotype was strongly validated, with participants fitting that profile having as much as 2.5-fold increased odds of abnormal bowel function (OR, 2.50; P < .001).
Importantly, the high stress/poor diet high-risk group also had significant reductions in gut microbial diversity compared with healthy controls (Shannon index, -0.18; P = .032).
The ‘Combination Is the Danger’
Of note, late-night eating that was independent of high stress was not associated with gut dysbiosis or bowel habits.
“People who only ate late showed no greater gut problems compared with those who didn’t, proving it’s not a stand-alone risk factor,” Dadigiri said. “The combination is the danger.”
“High stress plus late eating together more than doubled the odds of abnormal bowel habits, confirmed in both datasets and backed by measurably lower gut bacteria diversity,” she said.
More broadly, the findings provide evidence of a “chrononutrition-stress axis,” Dadigiri added.
“The results suggest that lifestyle interventions addressing both stress management and meal timing optimization may help improve gut health,” she said.
Study Limitations
Dadigiri noted that a limitation of the study was the difference in the types of data from the two cohorts.
“In the American Gut Project data, we didn’t have the allostatic load data per se, so we did look at factors such as economic inequality or psychological disorders like stress or depression that can increase the chronic stress on our body to serve as proxies for allostatic load,” she explained.
However, looking at the proxies and running the numbers reinforced “what we took as a direct allostatic load,” said Dadigiri. “That made us confident that what we were observing in phase 1 was also being reproduced in the phase 2.”
Additionally, due to the study’s observational nature, conclusions couldn’t be made regarding strict time cut-offs indicative of risk (such as eating anything after 9 PM), or having more or less than 25% of daily food after that hour, or if the nutritional composition of food matters, she added.
“In terms of next steps, and implementation of recommendations into clinical practice, we need prospective longitudinal studies and need to disentangle the issues of stress and sleep, which cannot be achieved in an observational study,” she said.
‘Hypothesis-Generating’
Commenting on the study, Loren Laine, MD, chair of the DDW meeting and chief of the Section of Digestive Diseases at Yale School of Medicine, New Haven, Connecticut, noted that “the ideas that atypical eating time and stress may cause GI symptoms is widely believed by the lay public, and so the issues raised in this abstract really have broad interest.”
With the noted caveats, however — along with the fact that phase 2 did not look at the time of eating — more research will be needed to understand the connection, Laine added.
“I would view the ideas as interesting and hypothesis-generating, but I would not say the results of this observational cross-sectional study should lead clinicians to change their practice at this time,” Laine told Medscape Medical News.
Dadigiri and Laine had no disclosures to report.
