Short-chain fatty acids and Firmicutes to Bacteroides ratio may be related in lean and obese humans

Scientists aren’t clear on the exact relationship between the Firmicutes to Bacteroides/Prevotella (F:B) ratio, fecal short-chain fatty acid (SCFA) levels, and obesity. This observational human study analyzed 3-day dietary intakes, physical activity levels, body mass index, fecal microbiota, and SCFAs in both lean and overweight/obese research participants (n=94).


They found that diet and physical activity levels were similar between groups. Compared to lean participants, those who were overweight/obese had higher SCFAs overall: higher fecal acetate, propionate, butyrate, and valerate. Researchers observed no significant differences in F:B ratio between the groups, but among all participants, higher Bacteroides/Prevotella counts were associated with lower fecal SCFAs. F:B ratio correlated with higher fecal SCFAs.

The results suggest that SCFAs and F:B ratio vary together and may be interrelated. Colonic fermentation patterns may be altered — but not necessarily by diet — leading to different SCFA concentrations in fecal samples of lean and overweight/obese humans.

This study is limited by the lack of mechanistic insight into these associations and its reliance on self-reported data about diet and physical activity.


Fernandes J, et al. (2014) Adiposity, gut microbiota and faecal short chain fatty acids are linked in adult humans. Nutrition & Diabetes doi:10.1038/nutd.2014.23


Paul Enck
Paul Enck
Prof. Dr. Paul Enck, Director of Research, Dept. of Psychosomatic Medicine and Psychotherapy, University Hospital Tübingen, Germany. His main interests are gut functions in health and disease, including functional and inflammatory bowel disorders, the role of the gut microbiota, regulation of eating and food intake and its disorders, of nausea, vomiting and motion sickness, and the psychophysiology and neurobiology of the placebo response, with specific emphasis on age and gender contributions. He has published more than 170 original data paper in scientific, peer-reviewed journals, and more than 250 book chapters and review articles. He is board member/treasurer of the European Society of Neurogastroenterology and Motility and of the German Society of Neurogastroenterology and Motility, and has served as reviewer for many international journals and grant agencies.