One-year calorie restriction impacts gut microbial composition but not its metabolic performance in obese adolescents

Recent evidence has disclosed a connection between gut microbial glycosidase activity and adiposity in obese. Here, we measured microbial -glucosidase and -galactosidase activities and sorted fluorescently labeled -galactosidase containing (GAL) microorganisms in faecal samples of eight lean andthirteen obese adolescents that followed a controlled calorie restriction program during one year. -galactosidase is a highly distributed functional trait, mainly expressed by members of Blautia, Bacteroides, Alcaligenes, Acinetobacter and Propionibacterium. Only long-term calorie restriction induced clear changes in the microbiota of obese adolescents. Long-term calorie restriction induced significant shifts in total and GAL gut microbiota, reducing the Firmicutes:Bacteroidetes ratio and enhancing the growth of beneficial microorganisms such as Bacteroides, Roseburia, Faecalibacterium and Clostridium XIVa. Moreover, the structure and composition of GAL community in obese after long-term calorie restriction was highly similar to that of lean adolescents. However, despite this high compositional similarity, microbial metabolic performance was different, split in two metabolic states at a body mass index value of 25. Our study shows that calorie restriction is a strong environmental force reshaping gut microbiota though its metabolic performance is linked to host's adiposity, suggesting that functional redundancy and metabolic plasticity are fundamental properties of gut microbial ecosystem.