['Transplanting a fecal sample from lean, healthy donors to obese recipients has been shown to improve metabolic syndrome symptoms. We therefore examined the gut microbiota in mice after administering a long-term, high-fat diet (HFD) supplemented with feces from lean mice through the fecal-oral route.', 'C57BL6/W mice were allowed to adapt to a non-specific pathogen free (SFP) environment for 2\xa0weeks before being divided into three groups of 16 animals. Animals were fed for 28\xa0weeks with a normal diet (ND), HFD or HFD supplemented with feces from ND-fed mice (HFDS). The composition of colonizing bacteria was evaluated in droppings collected under SPF conditions at the beginning of the study and at 12 and 28\xa0weeks using an 16S Metagenomics Kit on Ion PGM sequencer.', 'HFD and HFDS-fed mice attained (p\u2009<\u20090.05) greater body weights by weeks 6 and 5, respectively. HFDS-fed mice gained more weight than HFD-fed mice by week 25. Both species diversity and richness indices increased with time in HFDS mice only.'] Does prolonged transfer of feces from the lean mice modulate gut microbiota in obese mice?