Correlation between body mass index and gut concentrations of Lactobacillus reuteri, Bifidobacterium animalis, Methanobrevibacter smithii and Escherichia coliOriginal paper
Karen Pendergrass is a microbiome researcher specializing in microbiome-targeted interventions (MBTIs). She systematically analyzes scientific literature to identify microbial patterns, develop hypotheses, and validate interventions. As the founder of the Microbiome Signatures Database, she bridges microbiome research with clinical practice. In 2012, based on her own investigative research, she became the first documented case of FMT for Celiac Disease, four years before the first published case study.
Read MoreWhat was studied?
This study tested whether fecal concentrations of specific gut microbes correlate with body mass index (BMI) across a wide weight range. It extended an earlier case-control study by more than doubling the sample. Using quantitative PCR, the team measured Bacteroidetes, Firmicutes, Methanobrevibacter smithii, the Lactobacillus genus and five species, Escherichia coli, and Bifidobacterium animalis. Prevalence, concentration, and BMI correlations were analyzed. This article was later retracted.
Who was studied?
The cohort was 263 adults from Marseille, France, including 134 obese, 38 overweight, 76 lean, and 15 anorexic subjects. Average age was 50 years, and 52.5% were male. Of these, 137 came from the authors' previous study and 126 were newly enrolled. Anorexic patients met DSM-IV criteria and were more often younger women. This was a human cross-sectional analysis of single fecal samples.
What were the most important findings?
Fecal Lactobacillus reuteri correlated positively with BMI (r=0.44, p=0.004 among carriers) and rose in prevalence from anorexic to obese subjects. Its presence carried an odds ratio of 5.31 for obesity. Methanobrevibacter smithii and Bifidobacterium animalis were negatively associated with BMI, with B. animalis found in only 11% of people. Unexpectedly, E. coli concentration fell as BMI rose (p below 0.001), a novel finding. Firmicutes appeared in over 98.5% of subjects, Bacteroidetes in 67%.
What are the greatest implications of this study?
The authors conclude that species-level gut composition, not just broad phyla, tracks with body weight in a possibly dose-dependent way. Certain Lactobacillus species mark obesity while others and certain archaea mark leanness. The novel inverse link between E. coli and BMI was flagged as needing confirmation. Fecal sampling reflects the upper gut only indirectly, a stated limitation. Importantly, this article was subsequently retracted, so its conclusions should be treated with caution.