In the obesity-prone environment in which we live, no avenue for potentially health-promoting intervention should be ignored. One such avenue that has gained recent attention is the modulation of the gastrointestinal microbiota. Microbiota interventions have come into the spotlight because of the proposed relationships between the microbial community’s composition, function, and human health. One of the most common strategies for modulating the microbial community for potential health benefit is by dietary modifications, although antibiotics, microbial transplant, probiotics, and even exercise can also impact the gastrointestinal microbiome. With the emergence of evidence that timing of eating can impact health, it follows that the connection of eating behaviors to the gastrointestinal microbiota should be explored further. The objective of this research was to assess the links between circadian rhythms, timing of eating, and the human gastrointestinal microbiota. To accomplish this goal, a thorough review of the current literature was first conducted. Second, a cross-section of healthy, adult subjects was examined to determine the relative abundances of bacterial genera and concentrations of bacterial metabolites in fecal samples collected throughout the day. These variables were additionally assessed in relation to the subjects’ eating habits, including eating frequency, consumption of energy earlier in the day, and overnight fast duration. This study found strong evidence in the existing literature for the impact of circadian rhythms and eating behaviors on the gastrointestinal microbiota and health. Additionally, this work presents the results of a large, cross-sectional clinical study which found an association between time of day, microbiota composition and function, and eating behaviors. The results presented herein propose that this connection not only exists, but also could hold relevance for human health, with application to health-promoting interventions
