Disruptions in sleeping related to mealtime may contribute to an imbalance in the gut microbiome, and put individuals at a higher risk for metabolic diseases including diabetes, obesity and cancers. The aim of this pilot study was to investigate the relationships between late-night eating habits and sleep quality and duration, with gut microbiota (GM) profiles.

In this cross-sectional study, thirty-six men referred for treatment at the Tehran Gastroenterology and Hepatology Clinic were enrolled. In addition to the collection of demographic information, each participant completed different questionnaires to evaluate, medical history, physical activity level, late-night eating habits, sleep quality and sleep duration. The scores from these questionnaires were used to categorize the study participants into the following groups: sleep quality (good or poor), late night eating (yes or no) and sleep duration (<7 or ≥7 hours). Five grams of stool was also obtained from each participant for GM profiling analysis by sequencing.

The mean age of the study population was 42.1±1.6 years. Firmicutes and Actinobacteria were the two dominant phyla present in all participant samples. Differences in the relative abundance of GM at each taxonomic rank between study groups was largely insignificant. Only Erysipelotrichales at the order level, were found to be significantly different between individuals who had late-night eating habits and those who did not (p and q < 0.05). None of the other investigated parameters demonstrated a significant difference in GM profiles between participants of the study groups.

In this pilot study, we found Erysipelotrichales, a bacterial species previously linked to metabolic disorders and obesity, was more abundant in individuals with late-night eating habits. Studies with higher sample sizes are warranted to better delineate the possible effects of time of eating on microbial composition; to better understand the potential role of these species in disease risk.