The gut microbiota as an environmental factor that regulates fat storage

The human gut contains an immense number of microorganisms, collectively known as the microbiota. This community consists of at least 10¹³ citizens, is dominated by anaerobic bacteria, and includes ≈500-1,000 species whose collective genomes are estimated to contain 100 times more genes than our own human genome.

The microbiota can be viewed as a metabolic “organ” exquisitely tuned to our physiology that performs functions that we have not had to evolve on our own. These functions include the ability to process otherwise indigestible components of our diet, such as plant polysaccharides. Defining host signaling pathways regulated by the microbiota provides an opportunity to identify new therapeutic targets for promoting health.