Overall, obesity was associated with a significant reduction in bacteriome and virome diversity and richness, yet there was an increase in the richness of both virulence factors (VF) as well as antibiotic resistance genes (ARG) in the microbiome of people with obesity. It’s worth noting that an increase in VF richness has previously been observed among people with obesity, though adopting a high-fiber diet was shown to reduce VF abundance and its associated inflammation.
Although early studies pointed to an increase in the Firmicutes to Bacteroidetes (F/B) ratio among people with obesity, it is a finding has subsequently been called into question, and this meta-analysis also found this ratio was decreased rather than increased, and the authors suggest it should not be a reliable marker for obesity. Nine bacterial species were increased among people with obesity, including the first report of Eubacterium sp. CAG:274, as well as previously reported associations with Megamonas hypermegale, Ruminococcus gnavus, Allisonella histaminiformans, Collinsella stercoris and Collinsella intestinalis. Twenty-nine beneficial species were enriched among the control group, including Akkermansia muciniphila and Eubacterium eligens. A number of other findings emerged from this meta-analysis, including an upregulation of specific pathways in obesity, such as lipopolysaccharide (LPS) synthesis, as well as associations between the gut virome and obesity, though the functional role of many of the viral operational taxonomic units remain unknown.