The human gut microbiome and its role in obesity and the metabolic syndrome

The gut microbiota helps balance key vital functions for the host, including immunity and nutritional status. Studies have also linked the microbiome to human mood and behavior, as well as many gut disorders, eczema, and a number of systemic disorders (Azad et al., CMAJ 185:385–394, 2013). Changes in the gut microbiota composition and/or activity may be implicated in the control of inflammation, fat storage, and altered glucose response in obese patients. Dietary short-chain fatty acids appear to be “indirect nutrients” produced by the gut microbiota that can modulate adiposity and immunity as well as send signals to the gut to produce hormones that regulate appetite, permeability, and inflammation. Numerous data have been published regarding differences in the composition of the gut microbiota in obesity. Taken together, the data currently published suggest that specific changes in the gut microbiota occur in overweight or obese patients and are either positively or negatively linked with adiposity, inflammation, and glucose or lipid homeostasis. Manipulation of the microbiota though diet can promote healthy weight loss by altering gut function and metabolism. Probiotics and prebiotics are interesting research tools to assess the relevance of specific bacteria in obesity. Prebiotics may lessen obesity and related metabolic stress by modulating gut peptides involved in the control of appetite and gut barrier function