Obesity-associated gut microbiota is enriched in Lactobacillus reuteri and depleted in Bifidobacterium animalis and Methanobrevibacter smithiiOriginal 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 case-control study tested whether specific gut Lactobacillus and Bifidobacterium species differ between obese and lean adults. Both are marketed as probiotics, so the authors asked whether some might promote weight gain. Stool was analyzed by quantitative PCR for Firmicutes, Bacteroidetes, Methanobrevibacter smithii, Bifidobacterium animalis, and seven Lactobacillus species. Culture on Lactobacillus-selective LAMVAB medium was added. Logistic regression identified taxa linked to obesity. This article was later retracted.
Who was studied?
Participants were 115 French adults: 68 obese patients (body mass index over 30) and 47 lean controls (BMI 19-25). Obese patients came from two Marseille endocrinology units, and controls were healthy volunteers, predominantly Caucasian. Exclusions included recent antibiotics, bowel disease, and recent diarrhea. The groups matched on sex and height but not age. This was a human observational study using single stool samples.
What were the most important findings?
By quantitative PCR, Methanobrevibacter smithii and Bifidobacterium animalis were associated with normal weight, while Lactobacillus reuteri was associated with obesity. Adjusted odds ratios were 0.76 for M. smithii (p=0.03), 0.63 for B. animalis (p=0.056), and 1.79 for L. reuteri (p=0.04). M. smithii was less frequent in obese subjects (75% vs 89%, p=0.05). On culture, Lactobacillus paracasei and Lactobacillus plantarum appeared more often in controls. Culture and PCR agreed on enrichment of L. reuteri and depletion in the obese gut.
What are the greatest implications of this study?
The authors argue gut composition at the species level tracks with body weight, and that not all probiotic species behave alike. Some (B. animalis) associated with leanness, while L. reuteri associated with obesity. This raised caution about assuming all probiotics aid weight control. The authors stressed these are correlations, not proven causes, in the first such human species-level study. Importantly, this article was subsequently retracted, so its conclusions should be treated with caution.