Microbiota fasting-related changes ameliorate cognitive decline in obesity and boost ex vivo microglial function through the gut-brain axisOriginal 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 trial tested how diet-driven gut microbiota changes affect cognition in people with obesity, and whether brain immune cells called microglia mediate the effect. Adults were randomised to a Mediterranean diet, alternate-day fasting, or a ketogenic diet for three months. Cognition and faecal 16S rRNA microbiota were measured before and after. Blood inflammatory markers were also assessed. To test causation, human faecal samples were transplanted into mice, and microbiota-derived exosomes were applied to microglia-like cells in vitro.
Who was studied?
The human study enrolled 96 adults with obesity, randomised into Mediterranean diet, alternate-day fasting, and ketogenic diet groups. Mean ages were roughly 45-48 years, and most participants were women. Mechanistic work used mouse models. Twenty mice had their gut microbiota depleted with antibiotics, then received faecal transplants from individual human donors. Human monocyte-derived microglia-like cells were isolated from participants before and after fasting. Cognitive testing used Stroop, letter-and-number, trail making, and, in mice, novel object recognition tasks.
What were the most important findings?
Weight and BMI fell most in the ketogenic and fasting groups. Cognition improved most with alternate-day fasting: Stroop inhibitory control (p < 0.05) and working memory (p < 0.05) both rose, without worsening visual attention. Fasting lowered inflammation, with significant drops in ferritin and MCP-1 versus the other diets. Nine genera were depleted and nine enriched across the diets, with taxa correlating with cognitive scores. Microglia-like cells from fasting participants showed greater phagocytic capacity, motility, and wound healing. Mouse faecal transplants confirmed the fasting cognitive benefit was microbiota-dependent.
What are the greatest implications of this study?
The results position alternate-day fasting as a candidate strategy for obesity-related cognitive decline, acting through the gut-brain axis rather than weight loss alone. Cognition improved even though fasting and ketogenic diets produced similar weight loss. The transplant experiments suggest microbiota changes carry the cognitive benefit, with microglia serving as a downstream effector by boosting phagocytic and anti-inflammatory function. Because the human arm is a modest three-month trial and mechanisms rest partly on animal and in vitro models, longer studies are needed before clinical recommendations. The authors call the mechanism not yet fully elucidated.