Gut microbiota dysbiosis has been associated with the onset of several immune- and metabolic-related disorders. The specific role of exogenous factors leading to dysbiosis is still under investigation, and the primary factors contributing to gut microbiome dysbiosis and ultimately to human disease are not clear.

A new study, led by Dr. Boakai K. Robertson from the Department of Biological Sciences at the College of Science, Technology, Engineering and Mathematics from Alabama State University in Montgomery (Alabama, USA), has found that gut microbiome diversity is more influenced by a Westernized diet than a high body mass index.

By using a cross-sectional case-control study design (mixed method), the researchers studied how diet type and body mass index (BMI) correlated with gut microbiota diversity in randomly selected Alabama residents (n = 81) -including both females (n = 45) and males (n = 36)- aged 19-70 years in BMI categories of obese, overweight and normal-underweight. Stool samples and dietary surveys (including a 24-hour dietary recall, a participant generated list of favourite foods, and an assessment of the frequency of consumption of predetermined processed and fresh foods) were collected. Specifically, researchers were investigating variations in the abundance of different genera and species of bacteria in the Firmicutes and Bacteroidetes phyla in relation to BMI, food categories, and dietary groups (Westernized or healthy). Variations in the Firmicutes:Bacteroidetes ratio relative to BMI, food categories, and dietary groups at stratified abundance percentages were also assessed.

It was found that both the Bacteroidetes and Firmicutes phyla were evenly distributed across the study population. Besides this, although the Bacteroidetes phylum has previously been associated with a healthy weight, the researchers found this phylum was most prevalent among overweight or obese individuals consuming a Westernized diet type. Among the overweight-obese group, the presence of the genus Blautia – acetogen bacteria that can utilize a variety of substrates including sugars- as well as Lachnospiraceae and Prevotella copri were correlated with the increased consumption of highly processed foods and could be indicative of early gut microbiome dysbalance.

On the whole, the researchers found that processed food type had a greater effect upon the overall diversity of the gut microbiota than an increased BMI. These data suggest that a Westernized diet may be a critical factor in causing gut microbes dysbalance as compared to a high BMI.

In conclusion, although high BMI and a “Western” diet often co-occur, according to this study, diet seems to be more involved in lowering gut microbiota diversity as compared to increased BMI.



Davis SC, Yadav JS, Barrow SD, Robertson BK. Gut microbiome diversity influenced more by the Westernized dietary regime than the body mass index as assessed using effect size statistic. Microbiologyopen. 2017. doi: 10.1002/mbo3.476.