The human intestinal microbiota and its relationship to energy balance

The human gut microbiota can be pictured as a microbial organ placed within a host organ: it is composed of different cell lineages that have the capacity to communicate with one another and with the host. One major function of the microbiota is to degrade complex and otherwise indigestible components of the diet, such as polysaccharides. This process results in production of short-chain fatty acids that are readily absorbed and used as an energy source by the host. Studies in gnotobiotic mouse models are providing new details about how the gut microbiota can affect how calories from the diet are harvested and stored.