Effects of surgical and dietary weight loss therapy for obesity on gut microbiota composition and nutrient absorptionOriginal 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 compared how two weight-loss methods reshape the gut microbiota and nutrient absorption. One was laparoscopic sleeve gastrectomy, a bariatric surgery. The other was a very low calorie formula diet. Over six months, researchers tracked gut bacteria by shotgun sequencing, measured fecal short-chain fatty acids, fatty acids, and bile acids, and estimated the microbes' butyrate-making capacity.
Who was studied?
The core group was 10 obese women, average age 48, split into 5 who had sleeve gastrectomy and 5 on the very low calorie diet. Both groups lost nearly identical weight, about 24 percent, by six months. Complete longitudinal microbiome datasets covered 6 women (3 per group). An additional 10 subjects per group were analyzed for short-chain fatty acids. Only non-diabetic women of one enterotype were included to reduce variability.
What were the most important findings?
Despite equal weight loss, the two therapies moved the microbiota in opposite directions. Surgery raised the Bacteroidetes-to-Firmicutes ratio from 5.9 to 13.8, while the diet lowered it from 14.2 to 3.7. Surgery reduced butyrate-producing Firmicutes and the microbial capacity for butyrate fermentation. The diet increased both, driven by soluble fiber in the formula. Surgery also caused moderate malabsorption. Fecal fatty acid excretion rose from about 1,726 to 6,106 micromolar, and conjugated bile acids increased, pointing to altered bile acid circulation.
What are the greatest implications of this study?
The results challenge the idea that sleeve gastrectomy works purely by restricting food. It also drives malabsorption and reshapes bile acid handling and the microbiota. Because surgery lowered protective butyrate producers, the authors suggest soluble fiber supplementation might counteract that loss after the operation. The opposite diet effect highlights fiber as a tool to steer the gut toward beneficial bacteria during weight loss.