Researchers from the University of Nicosia in Cyprus explored how physical fitness and muscle mass relate to the gut microbiome. Their findings show that individuals with higher fitness and muscle mass tend to have greater levels of certain gut bacteria, including Alistipes, Bifidobacterium, Oscillibacter, and Faecalibacterium. The researchers reported these results in the journal Nutrients (Nutrients, 2024).
To reach these conclusions, the team conducted a meta-analysis of existing studies examining the link between body weight and gut microbial composition. They reviewed 60 studies sourced from major databases such as PubMed, Cochrane, and Scopus to assess patterns across diverse populations and study designs.
The analysis revealed a shift in the gut microbiome associated with obesity: a reduction in Bacteroidetes and a rise in Firmicutes when compared with individuals of normal weight. A clear association emerged between higher Firmicutes abundance and obesity-related metrics, including body mass index, fat mass, and waist circumference.
In contrast, a higher presence of Bacteroidetes correlated with healthier body composition and greater muscle mass. Athletes tended to show stronger representation of Bacteroidetes than individuals of average weight. The review also noted that bacteria such as Eubacterium, Lactobacillus, Megasphaera, Dorea, Streptococcus, and Dialister are more commonly found in higher numbers among those with obesity. Conversely, decreases in Alistipes, Bifidobacterium, Oscillibacter, and Faecalibacterium were observed when comparing with normal-weight groups.
Scientists propose that these associations may be partly explained by the gut-brain axis, a bidirectional communication network that links the gastrointestinal tract with the central nervous system. This signaling system can influence appetite, metabolism, and energy balance, helping to explain how gut microbes might affect weight and physical performance.
Another possible mechanism involves lipopolysaccharides, molecules on the outer membranes of certain Gram-negative bacteria. When these substances enter the bloodstream, they can trigger inflammatory responses that are often linked with obesity and metabolic changes. Understanding these pathways helps researchers clarify how the gut microbiome might contribute to or protect against obesity and related conditions.
Overall, the findings emphasize that the gut microbiome is not just a passenger but a potential player in weight regulation and fitness. Maintaining a diverse and balanced microbial community could support healthier body composition and exercise outcomes. Ongoing research aims to uncover how diet, physical activity, and other lifestyle factors shape gut bacteria and, in turn, influence health and performance (Nutrients, 2024).
Previously, scientists asked why certain bacteria become life-threatening under some circumstances. This line of inquiry continues to inform how microbial balance and the host’s biology interact to influence disease risk and overall well-being.