Obesity and the Microbiota

The enormous number and diversity of microorganisms in the human intestine contribute a diverse sec of functions, which complement the host for important features such as digestion of complex carbohydrates. Convventionalization of germ-free mice with a normal gut microbiota harvested from the distal intestine of conventionally raised mice leads to weight gain, obesity, and insulin resistance, suggesting that the gut microbiota may affect energy absorption. In addition, development of obesity in generically or diet-induced obese mice is associated with substantial changes in the composition and metabolic function of the gut microbiota. This trait is even transmissible as colonization of germ-free mice with an "obese gut microbiota" results in a greater increase in total body fat than colonization with a "lean gut microbiota." Recent studies in obese and lean twins suggest that an extensive core gut microbiome (ie, collective genome of the gut microbiota) exists, and that obese individuals exhibit reduced diversity and an altered representation of metabolic pathways in their microbiota. Moreover, the gut microbiota and its products directly regulate host gene expression and thereby control host energy expenditure and storage. Although human data are still in beginning stages, current findings support a concept chat the gut microbiome together with host genotype and life style might contribute to the development of obesity.