Chronic physiological stress caused by high blood pressure, a high body mass index, as well as high cholesterol and lipid levels, can disrupt bowel function and cause constipation or diarrhea, especially when combined with late night snacks. That's what a recent study led by a team at New York Medical College found.

For people already under stress, late-night eating delivers an added blow to gut health — it disrupts bowel function by reducing the diversity of the gut microbiome, the population of good bacteria that live in the gut — lead author, Harika Dadigiri, told TheDoctor.

People with high stress levels who ate late at night were more than twice as likely to report bowel problems than those who ate earlier.

The study drew on data from more than 11,000 participants in the National Health and Nutrition Examination Survey. People reporting high levels of stress who said they ate more than 25 percent of their daily calories after 9 pm were nearly two times more likely to develop constipation and diarrhea.

The results are similar to those in another study of 4,000 participants in the American Gut Project. Those who reported high stress levels and who ate late at night were more than 2.5 times more likely to report bowel problems than those who ate earlier. Their gut microbiomes also had less biodiversity.

What is it about meal timing that makes the effect of stress on the gut worse? The researchers see it as the result of a late meal or snack's effect on the two-way communication pathway involving hormones, the nervous system and gut bacteria that exists between the brain and the gut, though that is not yet proven.

Small consistent habits, such as keeping to a regular meal schedule, help support better digestive function over time.

These findings have implications for digestive health and the gut microbiome. They also highlight a growing awareness of chrononutrition, the effect of the body's circadian rhythms on how it processes food. “It's not what you eat but when you eat it, said Dadigiri, a resident physician at New York Medical College. Small consistent habits, such as keeping to a regular meal schedule, can help support better digestive function over time.

To those of us who often feel the urge for a late-night snack after a long day, Dadigiri is sympathetic, but offers some advice: “I am not the ice cream police!” she said, but it would be a good idea to try to have ice cream a little earlier in the day.

The research was presented at Digestive Disease Week (DDW) 2026. It has not yet been published in a peer-reviewed journal.

The study was observational — though it shows an association between eating habits, stress and gut health, it cannot prove a cause and effect relationship. To better understand how these three factors are connected, longitudinal studies that follow participants over time, including when and what they eat, are needed.